They also ruled that G_Date FN FALs are machineguns. Then they didn't. They ruled that open bolt Mac 10 and KG-9s were NFA machine guns because they were easily converted to full auto. And yes I do know as much about the functioning of the AR15-M16 platform as the ATF. Now they will say that the use of a bump stock when attached to a AR type semiautomatic firearm can initiate an automatic firing cycle by the single function of the trigger. I understand that the simulated automatic fire is caused by the movement of the trigger being bumped by a stationary finger and is in reality very rapid semi-auto fire. It won't matter. It's like attaching an electric motor to a trigger crank. It substitutes the actual trigger for the auto sear.
Used to be you could legally posses all manner of parts and pieces, like M2 carbine kits as long as they were not installed in your M1. Not any more. You can add the bump stock to the list.
“I understand that the simulated automatic fire is caused by the movement of the trigger being bumped by a stationary finger and is in reality very rapid semi-auto fire. It won’t matter.”
If you understand that how can you also say it creates an automatic weapon? The definition of auto is multiple rounds fired with a single trigger pull. Your logic is holding up.