A possible solution to this problem would be to add a mobile status option that essentially defers to, or matches the PC's status.
Then MS Teams would not have to guess what the user wants their status to be while in this mode. When the user steps away from their computer, their status will appear idle or away, but not offline. And when they shut down all their desktop instances (as for the day or weekend) they should then appear offline (although still able to receive messages on their phone).
Note that a user's phone activity does not indicate their availability in the same way that their PC activity does. There is a reason one of the options is "Appear offline". I personally don't want to broadcast that I can be reached. But I also don't want to appear offline when I come into work Monday morning (although it can be good for my personal productivity, :) ).
Adding this option would at least solve this problem for me. Thanks.