What is a narrow chest?
I've only heard people use narrow shoulders, I'm assuming it's the same thing?
No, narrow shoulders refers to a rabbit with shoulders that are narrow compared to its hindquarters; a good meat rabbit gradually widens slightly starting from the shoulder, through the midsection, to the hindquarter (in this case, looking at it from above). You can feel that by placing your thumb and fingers in a U over the shoulders and moving your hand backwards. A rabbit with a narrow shoulder will feel narrow and will often seem like it has a distinct break between the shoulder area and the flare of the rib cage. Sometimes a narrow shoulder is paired with low shoulder, which refers to a lack of depth in that area, easiest to see from a side view but also discernible by feel. A rabbit can also present with narrow shoulders because its spine is not correct; recently I had a fryer whose shoulders were pinched almost into an inverted V shape, and we found that its spine dove down so far between the shoulder blades that I had to wiggle a finger in between them to find the neck. A rabbit with shoulders that are narrow will sometimes fight being posed because the position can cause the shoulder bones to be pinched too close for comfort.
A narrow chest refers to the chest, not the shoulder, although a narrow chest can cause the rabbit to hold its shoulders strangely. I've found that the width of the chest depends on how "well-sprung" the ribcage is, as the sternum and true ribs comprise the chest. A narrow chest doesn't have as much room for the heart and lungs as a nice wide chest cavity. In fact this is one of the common reasons I see for rabbits fighting a pose: if the rabbit's chest is narrow, it's uncomfortable to be in the posed position with front legs flat on the table and head down. A narrow chest and/or small ribcage also means less meat. On my high-quality fryers and especially my roasters, there is actually enough meat on the ribcage to make it worth boning.
I don't understand your version of peaks early. I know it to be a line from knee straight up. And if that's what it is, then in the relaxed pic, it isn't forward.
The peak is where the spine stops rising from the shoulder and begins to descend towards the hindquarters. It's actually a structural feature, and many rabbits do not have a correct peak. In a natural position, some rabbits' peaks are forward and the spine slopes off after that. Some rabbits peak late, with a long, relatively flat rise from the shoulder to the hips - these rabbits usually look squared off over the hips and hindquarters. Some rabbits' spines rise, trail along in a relatively straight line, then slope off over the hindquarters. The knee is just a landmark to use to decide whether the peak is forward, correct, or late; lining the hind toes up under the knee aids in placing the rabbit in a position so that its skeleton is properly aligned to assess its shape.
Yes, you can "fake" the peak with an improper pose, sometimes, especially in compact breeds (e.g. Mini Rex) since their spines are especially pliable and rounded and there is very little room between their front and hind limbs. But even in the compact breeds, if you know what you're looking for, you can tell what's going on.
In the following photos, I'd call this as an early peak because the high point of the back starts just behind the shoulders; in fact the "peak" is a long flat stretch between the shoulders and the hips, which shows up in all three photos. Frequently when a rabbit has an early peak, you can continue the description as "peaks early, flattens out and slopes off toward the hindquarter." The sloping off (instead of being "well-rounded over the hips") is especially apparent in the first two photos, in which I'd call the rabbit overposed. In the top photo, the hind toes are almost touching the elbows, and the knee is behind the toes; I can't really see enough of the rabbit to detail the pose problems in the second photo. The bottom photo looks like the closest thing to a proper pose. Here it does look like the rabbit rounds nicely over the hindquarters, but you can see a somewhat long and low shoulder (which someone might suspect from the abrupt, almost vertical angle of the shoulder in the top image) and what appears as the longest flat stretch along the back before rounding off.
Below is an image of a more correct peak. My old guy Girdwood is age 5-1/2 and no longer has his tight muscle tone so he is a bit hollow-looking now, but his structure remains correct. He rises smoothly from the shoulder to a clear peak over his knee and hind foot, then rounds smoothly down to the table. His shoulder looks like it might be slightly long, and my older bucks do tend to grow longer in the shoulder, but it is not actually what's happened here. He moved his head - you can see his eye is not lined up with his front toes - which gave the illusion that there's a hesitation between the base of his ears and the curve of his back. But that disappears when his head and front feet are placed correctly; if you use your hand to feel there, there is not even a fingertip's space between his neck and his back.
Here are several more rabbits with correct peaks. You can see they are not being poked or prodded; they are quite comfortable in the correct pose, due to correct structure as well as training.
What is hollow loin?
The gap under the loin? It's not the thickness of loin. Or does a thick loin hide the natural gap? Immediately after the loin is very thin meat encasing the intestines, so I don't get how you not have some of that showing? I see a lot of fat rabbits being claimed to be full and in top condition, though.
A hollow loin is where there is a gap or indent between the loin and the hindquarters. A well-filled loin is deep and wide, and feels continuous with the hips, hind legs and lower hindquarter; you don't see any indent or feel the knees or any other "hitch" when you slide your hand from the shoulders to the hindquarters of the rabbit. A hollow loin can be due to lack of flesh condition, a small (narrow and/or shallow and/or tapered) loin, and/or improper posing, but I find it is quite often associated with pinched hindquarters. The latter causes the knees to stick out away from the body, making a hollow above the hind leg. No matter how you push or poke, it will show:
Here are some well-filled loins (and correct peaks), no manhandling required. The second and third rabbits, a Champagne D'Argent and a broken black Satin, are 8-9 weeks old.
I don't show, but I've been to a few to pick up rabbits. Rarely saw a judge that let the rabbit sit naturally and not shoved and poked and manhandled into a pose and tensed up with poking before being felt.
You might have seen something different if you'd stayed and listened to what the judges said as they posed each animal. Not all judges are good at it and maybe you just happened upon the wrong ones, but many times the "shoving and poking" is the judge's attempt to get an untrained or unhappy rabbit to sit in a position that will allow the best assessment. Rabbits are sometimes nervous when they're pulled out of the judging coops - especially if they've not been worked with and trained - and a good judge's handling actually can calm the rabbit. Other "pokes" are designed to encourage a rabbit to tense and then relax into a natural position. It can also allow assessment of flesh condition, as a lazy or overheated rabbit flopping on the table will not display its best qualities.
Apparently, I didn't close her nest properly. Quincy went out for a stroll. But didn't go far. After feeding, watering and adding new bottles to more drippers, she came over. Turns out, the two 15gal water troughs weren't good enough for her. She wanted her little cup water instead! 
lazy about breeding...I'm over it. I like bucks that know their job and do it, no piddling around. Hoping for a son to replace him with.
