I'm not aware of what the original devices looked like. Would they be allowable under the new rules?
Since we won't know the new rules until they are released (at the end of this month) NO ONE can answer that question at this time.
I think going down the rabbit hole claiming the new ATF ruling (when we know what it is) will discriminate against disabled people will only leave you in the bottom of a hole.
Our laws are supposed to ensure equality of OPPORTUNITY, not equality of OUTCOME.
Given what we know at the moment, and what we expect the ATF to rule, pistol "braces" will not be banned or made illegal, no matter what the ruling is. What can happen is that SOME items, currently classified as a brace and NOT a stock, will be reclassified as stocks. That does not make them prohibited items, it makes them REGULATED under the NFA, instead of non NFA regulated as they currently are.
Popular, easy, and convenient are generally of little or no concern to the law (and not just firearms laws). People often claim otherwise, but take a look at how the courts rule.
SOME braces may be affected by a change in the ATF ruling. ALL braces, and the idea of a brace will not and cannot be. It would require more than an ATF rule change to do that.
I remember a gadget I saw back in the 70s, (I've forgotten the name, and its probably long gone now) that was, literally a "universal" pistol brace. AND, it was designed to fit against your shoulder, it had a buttplate and a part of it even acted as a cheekpiece.
It would work for every handgun out there. It was not regulated, and there was never a hint of talk about NFA item. Because,
it did not attach to the gun! The forward end of the "stock" was a steel rod ending with a ball, which fitted into a socket on a wristband the shooter wore. Literally, the pistol wasn't braced, the shooter's ARM was.
That kind of system wouldn't appeal much to the UTubers who want to play SBR games using braces to avoid NFA regulation, but it is a fully functional brace allowing the benefits of rifle stock stability, and since it is neither a firearm, or part of one, avoids all firearms laws (that I know of).