Maybe, the NRA was trying to keep the question from reaching the Supremes to avoid the risk of th court blessing similar registration schemes being declared Constitutional.
They went this route instead:
Disarmed residents of the nation's capital, which is also the nation's murder capital, seem to have attracted a powerful ally in Sen. Orrin Hatch, Utah Republican. The D.C. Personal Protection Act, introduced by Mr. Hatch on July 15, would repeal the District's 27-year ban on handguns and lift prohibitions on carrying weapons in homes and businesses.
A DC law repeal would keep the Supremes from effectively extinguising the 2a as we know it.
They could be over thinking that however, but the stakes are indeed very high.
And it would also keep them from enforcing the second amendment as written. Meanwhile all of us not in DC will still have our RKBA infringed upon by various state and federal "Laws", that are not really laws since they are in violation of the Constitution.