every player is different. When im watching matches courtside, i notice that most players do that on the serve. it helps with controlling the pronation of the wrist at contact. On the forehand, berrettini has quite a wristy action so having that trigger finger does help with that too. I agree that his is pretty extreme. whatever works.Nothing to do with the new paint job here, but last night during the match with Aliassime the camera zoomed closed the way Berrettini holds the racquet on serve and when he hits the forehand and on both occasion i noticed the index of his right hand was way up than the rest of his hand. Is that how they hold the racquets?