It's not doing it on it's own, I believe what they're referring to is a a pre-configured distribution of a shell packaged with some distributions of Git, for some OSes.

There's a lot of different ways to install Git on a lot of different OSes, and some of them put helper shell scripts down by default.

That isn't Git installing things though, that is third-party Git distributions bundling things along with Git.

I'm aware, which is why I phrased it like I did. A lot of folks don't know or understand the distinction when they're installing Git (or installing something else that happens to bring Git with it).

The overarching point is that the shell itself is not installing anything at shell runtime. E.g. it's the Git Bash installer, not opening `bash`.

Yeah, even zsh doesn't do this by default