In the hundreds, maybe thousands of games my son has played in, there have been many instances where the pitcher starts to feel some type of discomfort. In that situation, they step off and have a moment to decide if it’s a concern that should remove them from the game. Now, in a worry to get a ball called on them within 20 seconds, they are going to probably move on to the next pitch and could potentially make things worse. That’s all I was thinking.
The main part of why the rule sucks is that it gives the umpire one more thing to decide a game.
It’s just an unnecessary rule in my opinion.
Sorry to completely baffle you