Eh. Gives the mystery folks an opportunity to use their quirks without others making preconceived notions they should abide by. Cide, unless you got an obvious mutation quirk, you couldn't tell most quirks from a glance anyways.

I was actually debating making Donny's quirk mysterious so the reveal that he's actually a blob monster is more impactful, but now I just kinda have to rely on dramatic irony when his meat suit is inevitably compromised.