Most installations use the “tests-passed” version of Discourse, which is updated typically several times a day, although each installation might be updated once a month or so.
Right now, the linked version is marked as 6 hours old, so I think it must be a very recent “tests-passed” version.
The actual tagged numbered versions of Discourse come out much less often, and for most people are not of great interest. For example, my forum is presently running 3.1.0.beta2, which would be one of a number of beta versions, except in reality I probably picked up a version a few days after that, which will have a few changes. (I updated in late January. It’s been an unusually long time since a beta.)
As an admin of a Discourse forum, I get notified when there’s a new beta.
Hope this helps: the summary is that everyone runs a leading-edge version, and version numbers are not so important.