Hm, I guess I got some things mixed up - sorry!
When I asked I wasn't thinking about a situation phosh has been in docked mode: It had an external keyboard connected, but no hdmi output.
That makes the situation even worth: the tiny screen is occupied by the virtual keyboard - even though I'm using an external one.
I guess we'd need more modes then "docked" and "undocked".
There should be a difference handling for attaching external monitors and external keyboards.