The Windows section stright-up says they don't really know what the situation is over there, and the macOS section says they couldn't find an official recommendation for non-GUI programs.

> Your advice re. Windows is also bad, for example, for a lot of x-platform tools I care more about x-platform consistency and would set the env var to the same ~/.config, e.g., it's much easier to do backup, and I don't care that there is some OS standard (which aren't great to be followed blindly)

If you just want to make your personal stuff do what you expect, then sure, by all means force everything to whatever you like, but that's not good general advice.