The thing about the different gender grounding contacts is a good point. However, it isn't hard to cut or break off the ground prong of a US plug, at least not the cheap hollow types I've seen.
I guees there was some design error. It's impossible to insert an ungrounded plug into a Schuko receptacle (unless you completely file it down as many people did, including myself) which would be perfectly safe, but it's not the least of a problem to insert a Schuko plug in an ungrounded receptacle which is pretty dangerous.
Only the pre-molded Schuko plugs have the hole for the french ground pin.
