I don't agree that rabbits always need hay if they are fed an appropriate pellet.
Over my years of raising rabbits I've heard
From the show people: If you feed hay or grass you won't have rabbits in quality condition for showing. It's easiest if you feed a hay free diet to maintain them in peak condition.
From the pet people: If you don't feed hay your rabbits will die!
Hogwash I say to both DEPENDING ON YOUR HERD and how it has adapted to your method of feeding. THIS is the key. Every rabbit herd adapts to how the owner feeds them. I know some herds that are fed beef cow hay and pellets and thrive. Others that are fed calf starter, grains, straw and a bit of pellets and thrive. Some that are fed pellets only ALL the time. And yet others that are fed timothy hay and pellets. And starting more I'm hearing of only fed produce and hay.... but the jury is still out on them as it's fairly new here.
.
My approach: Feed a varied diet. My diet for the rabbits includes occasional hay, mixed grains, pellets, and lots of produce from the grocery store I work at. Don't fuss too much if your hay is ONLY grass hay. Having a mixed grass hay I find it the best option.. as long as you know what the rabbit unfriendly weeds are!!! IN MY HERD.
In my herd hay is used as a "oh, I don't have produce today...here have some hay". "OH, it's the first major snow fall of the year.... have some hay." "oh, this stressful event happened (taken to a show, cleaned the entire rabbitry, neighbour cut down a tree... etc) ... have some hay."
My herd is a mix a show and pet quality rabbits. They move well into most any environment because I deliberately mix it up for them.
I've gotten rabbits from pellet only herds and found it nigh to impossible to help them through transition in my herd if they struggle with the move. I don't want other people having that same struggle.
You need to experiment with your herd to see what works for them. and it might take some time to finetune what you do. But you might just have to work it out in your mind how you want to feed and then keep the rabbits that do well on YOUR system of management. Over the years I've culled out the "I only want produce rabbits" and the "I don't like produce rabbits" and the "my kits get sick if I eat grain rabbits". I want rabbits that thrive on how I choose to feed... since I've seen how adaptable herds can to be how their owners manage them.