Someone in Fallout one, when talking about super mutants, says something akin to 'These aren't like regular mutants, they're hulking monsters.' Super mutants actually didn't start appearing until the master came along. Harold is actually a normal mutant Changed by an FEV strain from before the master restarted experimenting with FEV and creating super mutants. Harold talks about turning into a mutant at Mariposa around 3:50 ish. Bethesda didn't make him anything but a tree in the ground.
He even has specific dialogue stating he is a mutant Fallout 1. Why is he in Fallout 3? Cause Bethesda wanted to have him in the game as fan services and completely things up Also Bethesda made him a 'Special FEV Mutant' and not a ghoul. As for Harold, he was never a feral ghoul.
