It's when the point release was done[0]. Obviously not everything was new then. I'm assuming most people who package applications for Linux have an understanding of how Debian works.
We're not disagreeing — please stop trying to raise an argument where there is none!
My only reason for giving the point release date was to say that it's a supported release. You're reading a lot more into my tiny comment than I ever put into it.
Calling it "supported" in the context of the ability to build arbitrary software is misleading. It's supported by Debian for the particular packages included in Debian's package repositories - nothing less, nothing more.
[0]: https://www.debian.org/News/2019/20190216