On an acoustic piano, the metronome button no longer clicks when you press it. It decides whether "Keep the tempo" keeps clicking after the count-in.
The count-in always clicks, so you have a shared start. After that, the button decides. You can switch it before you start and while paused. It is the same setting as "Metronome while playing" in the player ⚙ and as the button on the digital piano.
If you practise one hand only and "Play other hand quietly" is on, Klavissimo plays the other hand along, as on the digital piano.
The player no longer has a metronome without the score.
What you see during a run
You find the button before you start and while paused in "Keep the tempo". During the count-in and the run, it is replaced by "Metronome on" or "Metronome off", so you know what comes next. In "Follow your playing" there is no metronome.
The "m" key switches the same setting. Because it is the setting from the digital piano, the button shows "on" unless you have changed it; before, it showed "off" on the acoustic path.