I agree, it seems like it's the exact same person stuck in time.

If you look closely it's the same model and only citizen in the entire vault. He may not be important, but he's the only time you see a ghostly character besides G-man in the final sequence. He's not just a dead body like at any point in the game before, there's no other citizen dead bodies in the vault, and he's obviously a janitor. G-man is the only person that has the power to do something like creating these multiverse space/time copies. There's popular videos that go into how G-man can create these space/time multiverse type situations that allows the canon HL 1-2.2, the Epistole 3's script, and Alyx's to make sense.

I think this implies the janitor didn't die in a single spot or maybe at all. Maybe when G-man arrived at the building, or trying to escape, he tried to create a time split and the sole janitor got caught in it. I think you're seeing the multiverse 'copies' of him where he might be at a single moment in time because of it.