Sides promote a striker of the ball not because the pitch is flat but because one bowler cannot be allowed to settle.
Sending a hitter up the order stopped being a batting decision
The old version of the idea was crude and honest. Field restrictions are on, the ball is hard, so push someone up who swings hard and accept that he might last four balls. Nobody thought about who was bowling. It was a general bet on the conditions.
That version is dead, and it died because the bowling side got better at planning. What replaced it is narrower and much more interesting: promotion as a matchup weapon, aimed at one bowler's over rather than at a phase of the innings. A left-hander goes in at three not because the ball is new but because the opposition's best off-spinner has four overs to bowl and the captain wants him bowling them to a batter who can hit against the turn. The pitch has nothing to do with it.
You can watch the counter-move now too. A captain who sees the promotion coming will hold that spinner back entirely, which means the promotion has already worked without a run being scored. It has taken a bowler out of the game. This is the part that never shows up in a scorecard, and it is the part that decides matches at the top level.
I would argue the whole idea needs renaming, because the traditional label suggests recklessness and what is actually happening is a fairly cold piece of arithmetic. If a bowler is due to concede fewer runs than the average bowler in the attack, removing his overs is worth something even when you lose a wicket doing it. The question is only whether the wicket costs more than the overs you displace, and against a team with a weak fifth bowler the answer is usually no.
Where it goes wrong is with the batter who has been promoted twice and dismissed twice, and who now walks out believing he has been asked to do something desperate. He has not. He has been asked to do a job with a defined start and end, and the coaching around that seems to lag well behind the tactic. Tell him which bowler he exists to attack and which one he is allowed to leave alone.
The teams doing this properly do not talk about it, for obvious reasons. Watch which bowler suddenly stops bowling in the seventh over and you will spot it anyway.

