Differentiation is one tire turning faster than the other or not is a straight line. Or, one tire with more load on it than the other. I or most anyone can hold your ARB locked with finger pulling on a tire lug and not very hard at that.
Simple test that everyone should do to educate themselves. Jack up one side, spin tire to show it unlocked, lock it, turn tire until you know it is locked. Put one finger on a lug, pull a bit and while holding that small bit of pressure, have someone unlock it with the switch. Your finger won't move. I have done that demonstration countless times back at camp after listening to folks "unlock" the front ARB to turn all day long on the trail. Ya'll ain't doing shit except wearing out the switch and the compressor because that bitch ain't unlocking with all that load on it.