This anon is correct.
This is not tied to the NPV. This addresses "rogue electors," which tend to be unlikely given that electors are chosen from each party.
So the Dems have a slate of electors and the Republicans have a slate of electors. When the state popular vote is tallied, all of the electors from the party candidate that won go to the Electoral College.
This ruling simply stipulates that states can attempt to mandate that rogue electors do not cast a vote for anyone other than the state's popular vote winner.