It is to settle actual conflicts by resort to principles of interpretation and bodies of law, such as the Constitution, statutes, regulations, etc.
Here, I suppose that it was NY's plan to deny a likely 2A friendly court the opportunity to hear the conflict by changing their law (and pretending that they conflict would never again exist), only when it appeared that a dispositive ruling (in the negative for NY) from the SCOTUS was likely.
I guess NY thought they could just stall and bleed the appellants dry and then ultimately change the law back, not having any negative SCOTUS opinion to say otherwise. It was a slimy move, and fortunately for the appellants, SCOTUS saw through that move.