Message 405722 - Python tracker

According to wikipedia, it was only the Big Sur beta that identified
itself as 10.16.  (And I observed this with the beta).  But the release
and, I think, the later Big Sur betas stopped doing that.

But I did eventually find a page showing a tweet that "documents" this behavior:
https://eclecticlight.co/2020/07/21/big-sur-is-both-10-16-and-11-0-its-official/

I guess obscure tweets have replaced documentation.