Earlier quoted context omitted.
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. [0]: https://www.debian.org/News/2019/20190216
> Obviously not everything was new then. Nothing was! Debian stable doesn't update packages (not even minor releases or bugfixes). They only backport security fixes or very critical bugfixes. Debian 9 was freezed on 2017-02-05. You'll have the version of every package from this date, point release don't change that.
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.