Question there is why would Companion need to be Origin character? :-/
Because that would make coop less seemless - the very poing o Origins is that you can smoothly transisiton from single-to coop - from 2 coop to 3-4 coop. You are playing a game and your buddies pop up - they join your game and take over companions, with content all being there because they are all designed to be playable. And all the playable characters are all hero (all sourcerers in D:OS2, all with super-unique parasite in BG3).
Of course, personally I would take dedicated companions, over origins, but it is, what it is.
