Everyone that has said the "loophole" is not real...
...is 100% correct. There is no "loophole" The law was intentionally written in a way as to protect the rights of the private, non-licensed citizen to sell their firearms.
This aspect of the law does get abused by licensed dealers wanting to avoid proper requirements of selling and save a few bucks.
That is why they need not to change the law, but instead crack down on unscrupulous dealers that try and ruin it for everyone else. Once you get that FFL you know you have to follow certain guidelines and you give up some of the privileges of the private citizen.