Well, if PA does not distinguish a moped from a motorized bicycle then I'm afraid you have it backwards.
Mopeds ( = motorized bicycle) must be titled, registered, plated, insured and ridden by licensed motorist. The fact that a motorized bicycle is a non-titled vehicle, then it cannot qualify for moped status.....thus illegal to ride in the streets of PA.
I'd love to have an attorney research this and provide us PA enthusiasts some clear direction.