While I am truly sorry your son hit some academic bumps, you can never know what bumps would have occurred on the other path - and you can bet there would have been some! Yes, there are absolutely some abstract concepts that are easier as the brain matures - I state this a lot when a middle school kid thinks they’re bad at math because they’re not ready for the level of abstraction they’re seeing. Give them another year or two and they will be ready - it has no bearing on whether they’re good at math or not.
BUT one cannot ignore a whole other set of facts, which is older students are much more likely to drop out and have an extremely hard time when they are the OLDEST and struggle. We’re seeing a whole bunch of kids who unfortunately hit Covid as their bump. Some gapped, some struggled with online formats, some just floundered. They’re now 24 and still haven’t finished undergrad. Redshirting has its own issues. I really think continuing to discuss being haunted by this shows some underlying issues that have nothing to do with the decision you made 20 years ago.