I believe that shipments to and from manufacturers and gunsmith for the purposes of repair or customization are specifically allowed under federal law (specifically GCA 1968). No room for BATFE interpretation there.
Indeed most gun control laws were passed by liberal congresses who did not want future conservative administrations to have any room to maneuver. They are therefore usually very specific.
In this case the statute did not define "transfer", so BATFE interpreted it to include sending a firearm to a 3rd party (not an employee) for business purposes. My guess is that someone in BATFE got to thinking how bad it would look for the agency if a prohibited person got a firearm this way and used it for something criminal. In their mind, better to just do a background check.
Right now, I am not worried about Federal problems. Yes, we need to remain alert - but there are not enough votes in congress to pass anything new. Gun control is so unpopular that a recent mailing to the democratic base - mistakenly mailed to my son - did not even mention it. Then there is Heller - and the question as to how far the Feds can go.......
But for those of us who live in California things are different. Here the Dems are racing to pas as many restrictive laws as they can before Heller applies against the states. That way our broke state can waste money fighting to take our rights away.
If you do live here, be gald. Very glad.