If Anakin’s fight with Dooku in Episode 3 is supposed to call back to the Throne Room fight in Episode 6, it would be cool if Dooku called back to how Vader “must obey his master.”

Anakin would be left with the question in his mind of why a Sith would do that, which would be resolved at the end of the movie when he’s in the suit, having lost everything, and still obeying Palpatine. It would also make Dooku more of an interesting character, and retroactively add something to this scene in Return of the Jedi.