To be honest, I doubt most rabbits are litter trained. Sure, many on here will be purely because people on here are bunny people! But most pet rabbits? I don't imagine many people, not being so into rabbits, spend time training them. ^-^
I know both my first two rabbits were not litter trained. Well, they sometimes sort of did when indoors - when they felt like it - but in their hutches, they never did. One used the entire hutch as a toilet, the other used a corner but would not tolerate a litter tray in there.
Both my current rabbits use a litter tray wonderfully when inside the house - but in their hutches... Barney sort of does. He just pees at the further corner and in doing so half misses the tray, but all his poops are in there. And Amber was incredibly offended or something, by its presence in her hutch... she scooped out ALL the material in there, piled it up into a mountain at the front part of the hutch and then flopped beside it... before peeing in two different places and pooping all over, as per usual.
It's just easier, sort of, to have them litter trained. But like yours, Barney always used his bed. So all it ever required was for me to clean out that smaller part of his hutch every day, and he was fine. Amber on the other hand... Ugh. There's no persuading her to make life easier for me!