"...Are these people just paranoid or just don't want to understand the laws of the ATF?"
Either or both... and in todays world paranoia is probably the main reason.
I accept either. You do your best to establish ID, that is what the law requires you to do as far as I recall.
It's the Fed authority that has established the system and it's available ways of alternative ID,,or not.
Nothing to do with the individual FFL. So you do your best. If you suspect something,of course you deny the transfer.
Like a bad check,,the person passing it off is the offender, not the one that gets unknowingly stuck with it.
..and like a check, if the FFL is a fake, the ID to back it up is most likely the same.
Seems as if the addition of 03FFL to EZCHECK would solve a lot.