This guy explains it all here:what’s up with the wristbands?
Though, this can not be replicated by everyone just because of index and middle finger length differences. Everybody has a "best position" for their anatomy IMO. I can not personally replicate the angle of the hand and be efficient because my middle finger is longer or index finger shorter. But the main idea is almost never using your thumb for support over pickups(that's where wristband comes in handy) or anywhere else and place it over strings to mute.