I think that though there is the basic liitter training ideas, that with bunnies, it is never as predictable as we hope for, and that there can be many solutions do the same issues. So i say, if you find something that works for you, then that is great. I know that part of the reason that hay is used in boxes is that not that it is a reward but that part of the digestiion process is to eat while pooping. I know with mine, they’ll munch on hay there while they poop, but they eat more hay from the hay bin that’s outside of box and they don’t poop outside of the box.
HOWEVER, Vivian who was used to having hay over her box at the shelter, at first did poop wherever she ate hay even if the hay was outside of her box, but for some reason, she figured it all out on her own, just makes sure to poop in her box regardless of where hay is.
For some bunnies, figuring out the their litter routine is a science!