I want to see every atf agent involved attach it to a firearm and fire it without hearing protection indoors, then decide if it's a silencer...
That's not the test for a complete silencer, and certainly not for a silencer part or component.
Silencer parts like a monocore ARE, by federal law definition, SILENCERS themselves, even without being assembled, even when they don't reduce the sound by a single decibel for the lack of a tube.