Gestures to reduce perceived tension do seem reasonable. It seems to be a habit that someone actually does unconsciously in any situation, not just in gambling. I also observe my friends when gambling; some tap the table with their fingers, and some bite their nails. Maybe that's their way of relieving tension during the game, or a way to stay focused.
It's true that some gestures like that are meant to relieve tension, but they can also be demonstrative so that other players can see them as easy targets Studying gestures is imperative for those who play poker. It's very helpful when a gesture tells us how the player is feeling whether they're a winner, a loser, or scared. There's always some kind of information that can be used to our advantage.
Gestures are a big trick, and they are especially important in poker, I have also seen when a player gets a very good hand, but then he deliberately makes a gesture that makes another player think he has a very bad hand, it confuses the other players, it is basically a deliberate strategy to send the wrong message, which causes the other players to make mistakes most of the time. And this whole thing, especially in poker, every movement, the eyes, these are very important information, but we have to be careful about who is acting and what they are really doing.