In my usage, the story is for myself first and foremost. Telling the story helps keep me organized and helps me remember what I've done and where I'm going. I don't need to know that I fixed a typo in a comment, I need to know what the changes are overall doing.
Sometimes I go down a dead end, reverse out, and leave a comment about why a different approach would be a dead end. I (and others) don't need a record of the work I did on that path, just the synthesis (an explanatory comment)
There are multiple systems for structuring commits, but the commit message body content approximates to the same in all of them. The classic advice is https://tbaggery.com/2008/04/19/a-note-about-git-commit-mess... , but I find https://www.conventionalcommits.org/en/v1.0.0/ useful for looking at the oneline log
To address this point:
> To checkpoint units of work as individual perceives them, helping them deal with interruptions (which include running out of work day).
Yes, commits can be used like this! But once you have a chunk of work ready for review, cleaning up the commit log/history, grouping related changes, and describing them is useful for maintaining the software.
I don't like squash merges personally, though they have their merits. But regardless, I would copy the commit subject/body content into the PR message, which then puts everything into the PR commit also, so technically the granular commits are less relevant when one merges, but occasionally are still useful to refer to
> In my usage, the story is for myself first and foremost.
But that's my point exactly. Unless you're exceptionally clear thinker, a story that's natural for you is not very good for anyone else. Your story is optimized for an audience of 1, developed interactively, and meant to help you in the now. The story for the team is meant to help them orient themselves after the fact. Turning one into the other is its own kind of work.
But then different people and teams have different ways of working. VC isn't the whole world. In some projects, I'd make "team story" commits directly, because I used a separate text file to note down my thoughts, and used that to keep me on track. So it's a different way of solving this problem.