That's good to know. I use a very simple and lightweight desktop called LXDE (or LXQt). It lacks such a user switching feature, but I wrote my own solution many years ago. I too have assigned multiple dummy users to some of the security critical applications like web browsers (3, each used with a different user

), email pgm, terminal shell, and some more, so that no user can access the data (ie. the home dir) of the other users. It's a security measure against online data theft, as well for limiting the access for this user to just this one application...
This method is not that secure compared to running a virtual machine for each such application, but is easier to do and eats much less resources (disk space, memory etc.)