They want to sell a different special edition for MY22. And they are bringing at least one new paint option, so one or more MY21 colors will go away.
The Mustangs all had 1965 Vin numbers. No 64 Vin numbers !Through the 80s, 90s and into the new century, the printing company I work for printed "authorized reprint" Ford Shop Manuals covering Mustang, Falcon, Fairlane, Cougar, Montego and T-Bird from years 1965 thru 1973. Thick books. And even though we only printed it once, there was a 1964 1/2 shop manual. Much fewer pages just to get service personnel started. Maybe some remember them being sold at rod runs or swap meets. The Mustang was a game changer. Every manufacturer had to create a "pony" car. The Bronco did the same. And now is again.
Edit. It was a stand alone supplement and also included with 1964 Comet Falcon shop manual