All of these machines and developers have legitimate access to the secret in question, though. Hence my framing of git as just a file storage format—any other mechanism provides the technical means for any of these machines or developers to publicize it. (And a few other simple mechanisms, like "scp the secret from another machine" or "copy/paste it with your terminal", have an increased risk of doing so by accident. Accidentally making a git repo public is generally unlikely.)

Why would that be a general rule. I track my personal passwords in git (using pass). I'm the only person with access to that repo. I just like to have a history - and the convenient way of moving files around and merging changes.