I am no scientist, but grooves are designed to move grass, dirt, and water away from the impact point where the ball meets the face. I was always taught that the ball doesn’t care what you do or what it feels like, only what the face is doing at impact. So in my opinion, your grooves should always be kept clean to give you the best chance for pure contact between the face of the club and the ball. This is something you can control… why add another potential variable that could impact ball flight? Spoken from a pure, non-scientific opinion.