Personally, I think it is a lot of hooie. As others have stated, I have documentation for all of my guns except the few that were inherited.
If by some strange fluke, one of my guns was purported to be stolen and subsequently confiscated, then I would take the person that I purchased it from to small claims court to recoup my loss.
In the big picture of life, I would want the gun returned to its rightful owner just as I would want any gun stolen from me returned.
In 40+ years of being in this hobby, I have posted full serial numbers and have never had any issues. If the govmt comes to my house someday
, my response will be: "Come on in, I'm your huckleberry" (just love that line!!!)