I'd never heard of S mode until my aging mother needed to get on a Zoom call with her doctor, and I couldn't install the app on her laptop because of it.
I set her up to use the web browser mode instead. Leaving it on was for the best at that point. I kinda figured S mode meant senior mode like for old people or something, idk. It certainly prevented her from installing anything bad by accident: and it was just a youtube and email thing for her anyway.