from what i read of that letter, they encourage FFL's to be a part of the transfer, but it does not make them mandatory in the transfer.
Ie, if you would like to make sure the person you are selling a firearm to is not a wacked out nut job loony with a record a mile long then you have the option of taking the gun to an FFL dealer and they can run the check for you on said individual.

"Hell with them fellows, buzzard got to eat same as a worm"
Josey Wales