That is the case, as current /e/OS builds for miatoll are based on Android 12 (S) and …
You are already missing security updates of several months. The last R build for miatoll is from February … https://images.ecloud.global/dev/miatoll/
Yes, that’s a concern, and it gets bigger every month.
For miatoll, with only dev builds available, not stable? I’m a realist, not an optimist.
Also considering …
Hmmm … That the updater App couldn’t do it in general was resolved quite a while ago, so in that sense the documentation needs to be updated (pinging @Manoj), even if in effect there will still be no OTA upgrade available for miatoll (the updater can’t offer what isn’t there).
There are no stable builds for miatoll currently.
OS OTA upgrades need to be prepared per device per upgrade step, which needs serious amounts of work by the developers. You can follow announcements in this category … https://community.e.foundation/tag/development-updates