Most likely, either MT misunderstood, which believe it or not, I actually doubt, or the Monkey that runs the Tesla webpages screwed up lol, and it was supposed to say:
*The indicated Plaid top speed requires a over-the-air software update, which will be available in Fall 2021.*
The reason that I believe MT, is that they confront this footnote in their article, and they also state Tesla said that these wheels have been recently validated at 200mph.
My personal guess, is not that the webmaster messed it up, but rather that Tesla had simply not validated these wheels and tires at 200mph in January, and that they haven't gotten around to updating the website yet.