And in that case, it would make sense, since one can't be assumed to know all the cases. But with “he” one can be assumed to know it, and I find it looking rat

And in that case, it would make sense, since one can't be assumed to know all the cases. But with “he” one can be assumed to know it, and I find it looking rather weird to state it. It's as though one put “Argentinian/Argentinians” in one's profile. — yes, I happen to know what the plural of “Argentinian” is.