Yeah, parahumans are way too varied to not do it on a case by case basis.
In fact, it almost seems like the majority of parahumans have unique powers – though there are plenty of parahumans carrying some of the most common powers, such as the Standard Alexandria Package (SAP), forcefields or super speed, there’s usually some sort of quirk to the specifics of how they work – Narwhal’s forcefields bypassing the Manton effect, Velocity’s super speed coming at the cost of his ability to affect the world, Glory Girl’s SAP coming with a body-covering forcefield instead of invulnerability, Tinkers having specialties – or an additional power that sets them apart from everyone else with that powerset (Glory Girl’s angelic aura on top of her SAP). Some powers are similar enough that the Protectorate can classify them systematically, but there’s still lots of variation that the system can’t describe.
That said, I’m talking with a limited set of data here. There may very well be hundreds or even thousands of people with the same powersets worldwide, and the story just hasn’t had a reason to bring that up. Still, this is how it looks right now.