Yeah, I wondered the same thing. It seems to be so. I don't think Apple ever states when an OS ends. It just stops getting updates. Safari 16 came out for newer OSes and Catalina was skipped. I imagine if there is some dangerous vulnerability between now and November, perhaps there could be one final security update.
Around here, "unsupported" normally refers to a device that is too old to run a specific version of macOS.
Back to the OS itself:
When Apple releases a new version of macOS, the old one receives (security) updates for about 2 years (at least that's what history taught us).
In the case of Catalina, with the soon to-be-released macOS Ventura, Catalina is expected to not receive updates anymore.
Or in other words, soon it will be like this:
Ventura: current version of macOS
Monterey: still 2 years of updates
Big Sur: still 1 year of updates
Catalina: end of updates
For the first time, maybe this is not such a big deal as Apple recently introduced XProtect Remediator for malware detection which should receive updates independently of the OS version.