OK, so I guess I'll come back to this one for a bit.
With regard to the last post, yes, I noted that. I also noted the part printed BEFORE that, which asked, "With regard to the Thompson/Center Contender pistol and carbine kit..."
The Contender differs in one significant way--you CAN attach a stock to the receiver of the firearm.
The Mech-Tech kit comes with a stock attached to the ACCESSORY, with no provision to attach it to the receiver of the Glock or 1911 pistol. That single factor is the most significant facet that makes the whole thing legal.
Or, so I was told by the ATF Agent....