I'm going to go against the grain here and say it can absolutely make a difference. My oldest son, non baseball, ended up in D1 athletics but got a bite from just one school. If he had taken a year, there is little doubt he would have been a state placer or champion given the year progression he made in skill level, physical maturity, and mental maturity. That would have given him more suitors, and provided him with more choices. Not only was he a year younger, but he was a late bloomer physically. So a double whammy. Not saying it's a route one should take, and it all worked out for us, but if I had to do it again with him, I would have given a year between middle school and high school.
Wech, no one is saying it can't make a difference. Most could argue that it would. But I don't think that was the OP's question and he doesn't say anything about possibly holding back a year. The points being made are..
1. Once you are in the recruiting process, don't allow it to be an excuse. Every player will face many hurdles to jump. Will the player attack and fly over them or hesitate and get hung up?
2. Recruiters don't care. You either have the skill set they are looking for when they need it or you don't. So, again, it doesn't do any good to dwell or get hung up on it. Do the best with what you have at any given time and keep working hard and smart at getting better.
Aslo, is it worth it in the big scheme of things to even think about ways to hold a kid back? For a few, maybe, but for most probably not. One of the scenario's OP describes is a great example. A kid is moved up due to academic acceleration. Well, if that has worked out, it sure wouldn't make sense to reverse that for athletics... far too many benefits otherwise in the big picture. I know this is a separate topic and one that has been discussed at length here on this site so I hope I am not starting thread drift.