Topic on User talk:1%macuser
An incomplete list of editing changes, among other changes to the site, can be seen here: https://www.pcgamingwiki.com/wiki/PCGamingWiki:Changelog
As for why pages tend to have the latest OS in the recommended section, if not blank? For the former, if it's not part of the official requirements, it's due to people moving things around as they see fit or a depreciated editing style where there could only be one OS listed in the minimum requirements, with any others moved to the recommended requirements section. For the latter? Usually it's because either 1) that part of the official recommended requirements section is identical to the minimum system requirements, and is therefore omitted per PCGamingWiki rules, or 2) there are no official recommended system requirements.
Finally, while the PCGamingWiki staff are aware of Valve's depreciation, there hasn't been any real discussion on deciding what, if any, action should be taken. If you think action needs to be taken now, then I reiterate my suggestion to join the Discord server and discuss it in the server's "development" channel (which, again, is open to the public despite the name). I make that suggestion simply because most discussion regarding articles and the operation and rules of the wiki take place on the Discord server in both a public and private, staff-only manner; thus, that'd be the best place to voice such things.