If I'm not mistaken, that's a parelli method and meant for the rider to be fair with cues and avoid just cropping/hitting with the rope the horse without a reason, and also to maintain the rythm of the cues. However, I wouldn't use it myself.
A good way how to distinguish a gallop from a fast canter is the momentum when the horse switches legs in mid air to go into a four-beat gait and it feels like he's hanging in the air for a second, and then suddenly shooting off much faster and with a very smooth movement, almost like gliding or flying over the road. You know the feeling when you experience it, it's unmistakeable. :) I cue my horse for gallop with going into two-point, extending one arm forwards and smooching once, if necessary. He then knows his job and does it gladly. :)