Doesn't really answer my question though: Do Beta releases usually appear here on F95? If they do, are they eventually followed by full releases?
Only if a leaker/uploader leaks it. On the other hand, some devs in this site have control of their game's OT and - possibly through the help of moderators - can control whether or not a leak gets posted in said thread. Usually though those games have public release dates that are not far off from the Beta release so people are willing to wait, or the early releases are usually buggier than a Bethesda game on release day that people don't bother leaking it and wait for the more polished release, or (and this is by no means an insult to those devs) the game isn't that popular enough for someone to leak it so people in the thread have to wait for the public release.
TL;DR, a beta release shows up only if it leaks and only if the dev controlling the OT doesn't strike it down. If no one leaks it or the beta is buggy, it's always the public release that gets posted or uploaded to replace the beta.