OC: I specified that they stipulated that it must cover the knees in ALL positions irregardless of the amount of inches below the knee, be it 4″, 3″, or 6″. I simply indicated — and you agreed — that for most people 4″ is minimally needed to reach that threshold.
Will less than 4″ ALWAYS cover the knees when sitting, walking stairs, and entering/exiting a vehicle? You’ve indicated above not. The Rabbonim, including all three that you’ve named, indicated that it must.