I think they either
A) Originally were then cut the idea early on.
B) Had a different unlock art style at first and then changed it.
Either way, they would have changed their minds during xbox development, so the PC characters wouldn't have any of this art lying around Edmunds lair. Hopefully I'm wrong about that last bit though.
I think they were working on the PC version first by looking at the old Steam Preview for the game (It had tim and the hominid)