I've seen people do similar with rifles (mostly) and one guy with a pistol.
Guy with a new CZ75 Compact 9MM. Started off the morning shooting consistently to the left of POA. After a few magazines his groups began to move to the right and finally centered on the target. I asked a couple times if he was still aiming at the center of the target and he confirmed he was not compensating for the bullet impact off to the left by aiming farther to the right.
At appleseeds I used to see people make sight adjustments early on Saturday morning to get their groups where they wanted them on the paper. Sometime Saturday afternoon, as they got more practice with their sling supported firing positions and trigger finger placement and cheek weld, etc., those groups would move again and they'd have to make another sight adjustment (this was at 25 meters, too.)