When our daughter was still living at home and smartphones were just barely getting smart we had a game, if you left your phone out it was fair game to respond to texts with absurd responses.
I occasionally respond to texts from my daughter on my wife’s phone, I can usually get away with one or two texts before. “Hi dad.”
That’s pretty much what squicks me out about mobile device user handling in a nutshell.
You can screw up and give someone access to a sensitive account on a real computer; but spinning up another user account or activating the guest account takes about 90 seconds, so that’s distinctly optional.
Over in mobile hell land there is only really support for a user account; along with a few cumbersome and generally inadequate tack-ons that can’t necessarily even be configured from the device(various kiosk options; android ‘work profile’, ‘shared ipad’ if you’ve got an MDM and a bunch of managed IDs); so you have little option but to either deny access entirely or walk straight into that problem.