They also said at WWDC 2020 on June 22 that they would have completed the transition within two years. So somewhere between 13 days and a very long time away.
I can totally see Apple spinning "December 2022" as being within two years of WWDC 2020.
Just looked it up and the first machines that shipped with M1 were released on November 10th so you might be right considering they never said 2 years from WWDC 2020 specifically.
Right, I just reviewed his comments at the end of the presentation, and it's easy to interpret Cook's comments as roughly 2 years from the first Mac at the end of 2020.