Would it be any less safe than a Molex connector? They sometimes still come with brand new PSUs for compatibility. They have 12 volt pins too (yellow wire) if I remember correctly that can be very loose. Back when they were more standard, I'd seen sparks go off after they touched a case's chassis, as a cable to the PSU could have multiple unused/unplugged Molex connectors on it just hanging somewhere. The older PSUs I've used never came with full covers for them, so wrapping them in electrical tape was the "fix".

Not a hardware guy, but I wonder if that's a factor in connector choice. Basically, if a significant fraction of PC building is done by teens or young adults building their gaming rig in their living room, with neither formal training nor oversight, do designers have to make sure this is "teenage proof"?

The GPU and PSU would have female ports and the cable would be male.

12V isn't dangerous to humans, but it could spark quite a bit if it hit the computer chassis.