Specifically, it displays "Raw Chicken" and "Raw Rabbit" as two mobs needing to be bred, instead of Chicken and Rabbit. This isn't an issue for other mobs, who correctly show their names.

because those mobs have food with the same name as the mob. it happens for a few advancements

Yes, that's unfortunate, but I can't do much unless I make special cases for each advancement, which will in turn break when a new MC version adds or removes or renames them. The advancements themselves have entries like "chicken", but no hint if a chicken (animal) or chicken (item) is wanted, so I just try a few possiblities until I find one.