One consequence of this, even though it only applies to the primary and even if it is reversed on appeal, is to effective kill any momentum the NPVIC might have had.
It really punctuated the fact that there is no such thing as a national vote when voters from different states aren’t even presented with the same choices. With the electoral college in place, this mostly doesn’t matter, but NPVIC would encourage the most partisan states to run up the score for their guy by any means possible.
Unless Maine also repeals their use of instant runoff voting for the presidential election, their own votes won’t count toward the national popular vote. The compact makes no provision for counting ranked ballots, and there isn’t really any fair way to do so anyway.