Most I supply music to seem to be fine with WAVs at 44/16 but some want them at 48/24 and then a couple want AIFs. For use in background music on TV why would it really matter?
It shouldn’t but probably more about compatibility and the fact 48/16 aif’s was the high def standard coming off of PRO Tools so many years ago (somebody correct me on this if I’m mistaken). I also think each library got use to accepting a format, from their beginning, and never bothered to change.