The rule distinguishes actions in the sand
Rule 12 permits digging the feet in to take a stance, but prohibits a practice swing touching bunker sand and certain other pre-stroke sand contacts. The rule is more specific than a simple ban on touching sand before the shot.
Watch two invented preparations. One player settles both feet slightly into the sand to stand. Another makes a rehearsal swing that brushes sand. Both disturb the surface, but they are different listed actions. The visible sand moving is not enough to give them the same ruling.
Keep the club’s path in view
A low camera may show the feet clearly while losing the clubhead just before it passes through the sand. Another angle may show a spray without revealing whether it came from the actual stroke or a practice movement. Timing and the body part or equipment involved matter.
The distinction helps explain why a player can spend time establishing footing and still keep the club hovering before the shot. It does not mean unlimited reshaping of a bunker is allowed: improving protected conditions remains a separate consideration. Read the actual preparation as a sequence, rather than counting every disturbance of sand as either always permitted or always prohibited.
Questions answered
Is all sand contact prohibited before a bunker shot?
No. The rule allows specified actions such as taking a stance.
What makes the rehearsal swing different?
Touching sand with the club during a practice swing is specifically restricted.
Sources & further reading
Official references for the subjects discussed. Service terms and device software can change.