Hmm... The article says: "On July 6, 2020, the U.S. Supreme Court ruled unanimously in both Chiafalo v. Washington and Colorado Department of State v. Baca that states may enforce laws to punish faithless electors." Is that what you mean? That seems like a "may" rather than a "must", and also talks about punishing them afterward rather than about voiding their vote.
SCOTUS has said that electors can be punished for not voting according to the rules laid out by the state. I'm not sure to what extent the various remedies available have been settled; that is, what can be done procedurally after a faithless elector casts their vote. AFAIK so far the effect has always been that their vote was counted and certified.
They’re actually not. Thanks to a (trump era) SCOTUS ruling, EC votes are now fully regulated by the states.