I have a bit more time on FBS that you, but what it really boils down to is preference, just like so may things in this hobby. It's whatever works for you and your circumstances. I shouldn't have used the word "wrong"....my bad.
It's my opinion that I want the machine to pick the cleanest channel regardless of where the coil is, which to me means that if I allow it to pick one with the coil further from the ground than I'm likely to swing (but not too high), then I'm exposing it to any EMI that may be an issue and it can make the proper choice. If I were to do it on the ground, then a certain amount of the coil is effectively shielded, meaning that if not constantly scrubbing the ground, the posibility of interference not delt with goes up. I can't even say that I hunt many places where ground scrubbing is possible with an open coil.
I hunt with an Explorer SE, and guru Bryce Brown likes hunting with his sensitivity @ 26 Auto, yet others (including Sabisch) say that the machine adjusts too much so you should never run in Auto for maximum depth. So who's wrong really? All have good finds to back up their positions.
Again I have to say that it's up to you, on your ground, with your EMI, your headphones, your threshold preference, your coil selection, etc... Experiment to find what works. And what works one place might not work at another, just as what works for one of us might not work for another.