Rumor control says they came from Israel and were cut into two pieces with a saw, the pieces wired together and stored in a 55 gallon drum in used motor oil. Proper demil procedures apparently require them to be torch cut into three pieces. Other rumors say that the selector stud was moved forward so that the connector couldn't trip the sear for full auto and it was considered readily convertable back to full auto.
I personally asked one of the Tech Branch guys at the Shot Show about the M14 rewelds and he indicated that if it isn't torch cut into three pieces and the selector stud removed, and rebuild would be illegal.
As for the white male discrimination non-issue, most of these receivers were probably purchased by white males. The receivers are the subject of the enforcement effort. They are being confiscated. As far as I know, nobody who turns over their post-86 machineguns (the MKS M14s) is being charged.
Anyone holding one of these receivers built up into a complete rifle should strip it of all parts including the barrel and give the BATF a stripped receiver. MK-Specialties should then give them one of the new forged receivers with a credit for the difference in price, and if the original receiver was sold as a complete rifle, install all the old parts on them free of charge.