My guess is he means FFL transfer with a 4473 kind of "binds it" to you in a sense. I did a bill of sale for a private purchase, so it's not "registered" in the govt sense, but the other party and I (if he kept his copy) has a signed record of it.
Reminds me of that guy who was posting on here that he wanted to buy "a 9mm or 45 for about $500, FTF only" - that threw up the red flags. Didn't care the model or caliber, lol.
When someone asked if he had his P&R (required for pistols if you don't know the buyer), he replied, "I don't need one."