Unfortunately, that's not what I've seen. Ask Randy Weaver. Having a SBS and selling to an ATF informant is what started the whole mess with him and his family.
What you're saying does happen quite frequently. But the ATF also prosecutes for the "rule" violations as well. Isn't that what happened to the two guys in the key card case? They were just selling metal cards with parts drawings on them.
The ATF is out of control and needs to be stopped.