It’s interesting because I once read something about the Satanic elite having a six-finger mutation gene (or something to that effect).

Don’t ask for a source. It was way back in the heyday of the internet.

I'm fairly certain its intentional to let them easily filter against deepfakes or polluting the training set.

AI is certainly capable of learning these details correctly, it must be by design that they get it to generate "eldritch hands" and funky eyes.