Every side of the political spectrum has used every technicality they can possibly find in the Constitution to justify all sorts of abuse of the rules. This is how the Constitution evolves, and the rules of order. Every Article, Clause and Amendment has been pored over multiple times to find language that supports or denies one side over the other.
You will find all pertinent language in the US Constitution and the US Code
here, and there is not one shred of language I can find prescribing how the Electors vote. Such a maneuver seems entirely supported by law.