The letter of the law hasn't changed, just some person's opinion on how the law
should be enforced. It just so happens that this "some person" and his pals have the ability to really wreck your life.
(7) The term “rifle” means a weapon designed or redesigned, made or remade, and intended to be fired from the shoulder and designed or redesigned and made or remade to use the energy of an explosive to fire only a single projectile through a rifled bore for each single pull of the trigger.
(8 ) The term “short-barreled rifle” means a rifle having one or more barrels less than sixteen inches in length and any weapon made from a rifle (whether by alteration, modification, or otherwise) if such weapon, as modified, has an overall length of less than twenty-six inches.
(29) The term “handgun” means— (A) a firearm which has a short stock and is designed to be held and fired by the use of a single hand;
The whole thing is ridiculous. The original firearm is, as a pistol, designed to be held and fired with one hand according to ATF. The brace is designed to be held and fired with one hand according to ATF. The legal definitions above don't say a single thing about "able to be fired from the shoulder" or "able to be fired with more than one hand."
Kingery's letter (first reversal) was about as stupid as saying that using a two handed grip on a pistol makes it an AOW!
Either way, aren't these letters only "good" for the person they are sent to, and even then, they aren't binding since they're just an opinion? You might be able to beat the rap, but not the ride... the final decision would fall to the courts if some LEO wanted to send you up for putting it against your shoulder. The plain language above would hopefully be... plain... to a judge/jury.