Just so I'm understanding this absurdity right...
If an end user separately buys all the parts needed to later self-manufacture a complete firearm, including an unfinished receiver that the ATF has explicitly stated is NOT a firearm until machined by said user, the end user HAS NOT bought a firearm according to the ATF.
If an end user buys all the parts needed to later self-manufacture a complete firearm together as a one line item kit, including an unfinished receiver that the ATF has explicitly stated is NOT a firearm until machined by said user, the end user HAS bought a firearm according to the ATF.
Is the issue the fact that this was sold/marketed as a kit by Polymer80? Or that it all came from the same source? If an end user buys all the parts that would go into the kit from Polymer80, but as separate line items, would the ATF then apparently not have a grievance?