[zbuf]

I think you're assuming that all software results in a single "release manager".

In many environments, multiple branches of software are deployed and maintained at the same time.

Even your example with Linux; I don't think that is correct -- Linus doesn't tag the stable branches, and others. There is a centralised agreement of how the version numbers are maintained though.

[da-x]

My example is relevant to tagging in branches that may merge back into the main one. The stable branches in Linux are cherry-pick branches that don't get merged back and therefore creating tags there is harmless.