<< Bearer of bad news: it's not that special. Most of my snakes will stop and chill for a minute or 2 when I start rubbing their chins. I've shown others to do it with snakes as well. It almost puts them in a trance. I guess their chins are sensitive to vibration when they get it massaged in a sense, they get kinda like a dog when you find that magic scratch spot which gets their leg kicking. Then when you stop, they start tongue flcking again and look around to see why it stopped.
One difference is mine don't raise their heads, they press down more and try to get more chin surface on my fingers.