Probably he means that Debian stable is outdated by definition (e.g., Debian 12 it just released to stable, and has Gnome 43 instead of 44), and to stay on top of new versions you would eventually rely on flatpak.

However this is a false problem, because if you want a updated version, you just change your update channel from ‘stable’ to ‘testing’ in the sources.list conf file etc voilà you have a rolling release with fresh stuff.