He is just mainly saying that its the ffl item for the gun and the only thing you cannot just buy and have shipped to your house. Im not positive but if a gun was build as an "SBR", something would have to be registered. Im just not sure if the registered part would be the upper or receiver. It doesn't matter what state your in at that point.
Regardless, throw this on a lower with the pistol buffer tube and call it a day. Don't have to mess with anything at that point