Just looking at the video DB provided I would say the device modifies the action around the sear. The report mentions springs. I’d guess the device bumps the sear down before it can engage the bolt.
The BATF is real touchy about messing with sears. Anybody with an AR15 type rifle needs to be aware of that fact.
W.T.F.?? The sear is inside, the AA is external and does not enter the insides where the sear is. Are you stumping for the BATFE? a plant?
It works on exactly the same principal as the "Helfire" and other completely legal devices. It uses the recoil motion to release and re-depress the trigger, simulating full auto, in a semi-auto action, which, by statute, is completely legal. In order for the BATFE to legally ban these they need to take the NFA law that defined "automatic" or "full automatic" back to congress to get it changed to what they want it to say. Until then, the device is legal, no matter how badly they want it to be otherwise....