Well, it can be narrowed down to:
a) It applies only to one weapon (like shillelagh);
or
b) It applies to all weapons you are proficent with (like Monk).
If a) is correct, and hexblade is added to BG3 at some point in the future, then it might apply to two weapons.
I don't see how your pure conjecture is any better than saying "Here's how Jeremy Crawford says it works in PnP."
