So let's say that you are moving a ball around with ball in hand,and are using the stick/ferrule to position it. Many people do that. You push it with your tip accidently instead of the side of the shaft/ferrule, nothing else gets hit, no rail, no other ball. Is that now a "shot" and you fouled? Or does the "shot" start when you get in stance and start the stoke (like the rule in baseball where you check your swing and it's not a strike till you break the plane).
Under both WSR and BCAPL rules, the test to be applied is: is it a forward motion of the cue that would normally be considered a shot?
Put another way - would you consider it a shot at any other time? If so, then the game has begun, because, for the purposes of this rule, and as Bob observed earlier, there is no difference between a break shot and any other shot!!
While some rule sets (APA and maybe others), apply a different standard to break shots than other shots, WSR and BCAPL do not. For the purposes of determining a foul, once a stroke is taken, it's just another shot.
Now - before a stroke has been taken on a break shot, or any other shot when you have BIH, you may do virtually anything you want with any part of your hand, cue or cue tip, and it will be legal provided it is not a forward-stroke motion with contact with the tip. The instant that happens, it becomes a shot and subject to all the normal rules of the game reagrding fouls.
So while you have BIH, yes you may use your cue tip to adjust the position of the ball - again, as long as it is not a forward stroke motion. The actual part of the tip used is not relevant.
Stance, body position, establishment of a bridge, etc., are all irrelevant.
Buddy