They are trying a backdoor ban by regulating the use of braces so strictly that they will become much less practical to use.
August is the expected roll out of the new rules.
I always said the roll out of the new e-file system was in perpetration for such a thing.
No, my understanding is it is not the braces per-say they're banning, but they're changing the definition of what constitutes a pistol per administrative fiat with various weight, length, etc, components that even result in things like the Desert Eagle classifying as an SBR. So when the firearm itself is defined as no longer a pistol under these new definitions, then the brace is irrelevant. Yes, it's a can of worms making a sizeable portion of the firearms community potential felons overnight.
Additionally, they are also trying to change the definition of a firearm itself after at least a few AR-related prosecutions have been dropped due to the AR lower receiver not technically being a firearm in the strictest definition of current law. I don't fully follow/understand what it is exactly that's happening/the BATF is wanting to do, but they may be trying to make both upper and lower receivers collectively a firearm, or maybe changing the upper to a receiver to be serialized for a new registry/accounting (on ruger 10/22s for instance, the upper is the receiver even though lower trigger group housing is effectively the same as an AR lower), etc.
Whole thing is going to be a mess. The only reason they pulled the pistol brace stuff in 2020 when they pushed was Trump Admin pushed back on them -- Biden is encouraging BATF to be bad actors.