Amy, I really don't doubt that could be the case, but again, I think it goes back to bloodlines and several other factors. The consumption rates of certain types of feed are bound to be different than others, too.
I like to think of it like this. There are certain types foods that we as humans will fill up on faster than others, even though by weight, they are quite similar. It explains why all the feed companies tell you to feed by weight, not volume. You have to adjust the amounts you feed to match how much the rabbit in question is consuming. The feed I used on my foster litter was a cut-rate feed in comparison to some of the other name brand feeds on the market. Had I been feeding something like Heinold Starter Formula or another similar product, the consumption rates would have been quite different. Because the ingredients were different, an argument could easily be made that the results would have been different as well.