@valleyforge IMO a PDW is usually a SMG that shoots fancy expensive AP PDW ammo. 4.6 and 5.7. It's something that was intended to replace SMG's and carbines, but couldn't because it's too expensive to add the ammo to military supply chains.
@Diptchip hey forgotten weapons posted a q&a video this morning making exactly this argument!
@Diptchip I think it's more of a role thing. So smgs are designed for suppression and for firepower at short range whereas pdws are designed to be carried by support personnel for defense. So the original cz scorpion is definitely a pdw even through it's in 32acp. Hell even an m1 carbine fits this description