Dual Extruder - Proximity sensor used and required?

Hi folks,

Can someone explain to me whether the proximity sensor is used? I destroyed mine and replaced it on my own. After I attached it and ran first calibration, it looks like the artisan is just calibrating with the left nozzle as it does when Z level calibration and will not use the proximity at all.
Is there any use of the proximity sensor? Why is it there?

It’s for leveling on metal (like the magnetic sheet of the 2.0).
Artisan has a Glas bed as well, correct?