I do believe you about the "updated" part, and that's a constant hazard with linking to "latest" or "main" of anything. But I don't know why you'd then change the actual file in the URL, since the original comment was citing "podman-systemd.unit.5.html" <https://docs.podman.io/en/v5.6.1/markdown/podman-systemd.uni...> and you've chosen to cite quadlet.7
Not OP but "podman-systemd.unit.5" used to be the primary Quadlet documentation (a remnant of when it was podman-generate-systemd perhaps?) with every Quadlet file type (.container, .volume, .network, etwc) documented on one page.
The new docs split that out into separate podman-container/volume/etc.unit(5) pages, with quadlet.7 being the index page. So they're still linking to the same documentation, just the organization happened to change underneath them.
Not podman user (but currently trying to install to give it a shot), this comment stream shows how even the documentation "randomly disappearing" on a project that claims in production-ready or stable state. (Or lack thereof)
On the contrary, docker documentation *is* stable, I had bookmarks from 10-years ago on the *latest* editions, that still work today. The final link may have changed, but at least, there is a redirect (or a text showing that has been moved) instead of plain 404/not-found.
This is a crucial part of the quality applications offer. There might've been 100s of podmans probably since Docker was launched more than 10 years ago, but none came close to maintain high-quality of documentation and user-interface (ie. cli commands, switches). Especially in the backward-compatible way.