Those of us who will have to throw away a $350+ keyboard used for less than one year will emphasize that the video in no way made clear that only a new generation magic keyboard will suffice. The emphasis in the video at the point was about a new exciting color - white - but no specific effects graphics showing us how to throw away a nine month old keyboard that has no trade-in value and not worth the effort on swap webs.
However, the following statement in the upthread article will generate some confusion until a final word from Apple although on their web they do now clearly define a #5 magic keyboard for the 2021 iPad Pro:
"And according to the documentation provided to the Apple Stores that we have been able to consult, the old Magic Keyboard is not compatible with the large iPad Pros of 2021."