There's a certain amount of showmanship going on there... If I drop my bass E string down an octave so I can get a super low E and then take it back up, who cares... Mostly that's what you'll see... Fat E up or down or A string from open G to Double dropped D...

Of course there are also open tuning where the Fat E tuner can be used much like fretting...

But it's more show than go... Shouldn't confess to that but I have...

B~