But now the commit message (in the example) is wrong. Or at least, strange. Because it says both that ls was added and also advanced ls. But the actual commit itself is only the "ls -al".

It seems like it would make more sense to just commit it in this case.

nope... they are just dummy texts. think about its a kind of notebook. helps you to remember all the changes while making the commit... pops those notes in to your commit message.

I see, but it is in the actual commit message right, in the asciinema I mean.

And I use SourceTree, so after a big commit I still go through the diff line by line. So I've never had to remember details like that for the last year.

What would be the advantage here over committing locally and then rebasing?

this... I commit all the time locally.. "Saving progress on feature X" or whatever... then when I go to push upstream you just rebase.