Dante thank you for 2 excellent posts that clearly explain the situation with Infernals.
I'd like to add one point.
Dante wrote:
I don't think I've seen any examples of native vs. extra-planar mattering yet in the new rules.
The spell Banishment would seem to be intended to work only on extra-planar creatures. While the rules as written seems to indicate that it can also work on Native Infernals (and Elementals and Celestials).
You are correct it doesn't matter in the rules, but I think this should matter.
I think even with the game changes it's important to keep the distinction between Bound/Unbound and Native/Extra-Planar on stat blocks.
I know we can't go back and easily change the Crusade Arc modules, and with discussion on this forum about the possibility of retiring those modules, there is no real need.
But I hope stat block writers going forward remember to add that piece of information.