As much as the ATF might be held in disregard, they were also doing what they were told by their Boss. Now there is a new Boss. Winning is a good thing.
Much of the Open Letter was misinterpreted, and to add to that the ATF has a history of writing things in their own legalese, which means it doesn't conform to Jimmy Carter's Plain Language initiative of old. There is also another aspect of the issue many won't discuss. Most of the "enforcement" was coming from people NOT in the employ of the ATF, and when they attempted to do so asking for the ATF to back them up, it became difficult.
Your local range knowitall and some Range Officers were acting out of their appointed duties and working pro bono for the ATF. They know who they are, we have seen the enemy and he is us in a lot of circumstances.
All this interpretation on the spot by outsiders generated more questions than help and the ATF just needed it to stop. Absent any cases filed I can't say for sure, but I expect there were some who were willing to launch some legal suits to clear up just exactly what was and wasn't allowed. If you read the new letter even the ATF admits there were legal interpretations for which they had no grounds. If it went to court that would be difficult to overcome.
A lot of posters on the internet derided each other when different interpretations came up and would jokingly suggest 'Well, why don't you write a letter?" mocking them for causing the ruckus in the first place. I'm thinking more than a few DID, along with manufacturers, and it was getting obnoxious to answer the same questions over and over again.
Might as well lay the thing to rest to some degree and move on.
It's also not the central focus of the letter - it does explain the shouldering issue, most of the letter is about what can and can't be done with the attachment itself. If it's clamped down and extends the length of pull, that intends for it to be a shoulder stock, not wrist brace, so that is no longer allowed. If you leave the straps off it diminishes it's job as a brace making it more like a stock, not allowed. That language is clear and specific.
Brace owners are not getting a free shoulder stock Stamp out of this. It's a brace and remains a brace, it has to be positioned and equipped to use it like a brace, and I foresee the ATF insisting the newer versions enhance it being a brace more than stock.
I for one would not count on various forums suddenly changing their policies over pictures or content of a post which explains intent. Why? Once again, we are sometimes our own worst enemy. We play the game fair and toe the legal lines even dealing with unConstitutional laws which restrict our rights. And our enemies exploit that any way they can.