Changing the size of the Supreme Court is exactly what Republicans did in 2016. Also from 2016: If Clinton Wins, Republicans Suggest Shrinking Size of Supreme Court
Of course, Republicans have been active in doing this version of altering the courts. In addition to Garland, they are proud of doing it across the board.
Also: Biden is again asked why voters don’t deserve to know his views on court packing. He responds: “The only court packing going on right now is going on with Republicans packing the court right now ... I’m going to stay focused on it so we don’t take our eyes off the ball here."