Maybe I remember wrong, but my memory is that at one point MacOS had zsh as the default and then switched to BASH, and then maybe back to zsh again. But, since Internet search is broken these days, I can’t find anything about that.
All I can really tell you is that I remember seeing a message about the new default being zsh, and that was back in 2020 or maybe 2021. So it def switched from something else to zsh, but whether it was bash -> zsh or zsh -> bash -> zsh…shrug
Maybe I remember wrong, but my memory is that at one point MacOS had zsh as the default and then switched to BASH, and then maybe back to zsh again. But, since Internet search is broken these days, I can’t find anything about that.
All I can really tell you is that I remember seeing a message about the new default being zsh, and that was back in 2020 or maybe 2021. So it def switched from something else to zsh, but whether it was bash -> zsh or zsh -> bash -> zsh…shrug