Even the best batter in the league goes to batting practice, studies what other good batters do, takes advice from coaches, some will likely study sports scienc

Even the best batter in the league goes to batting practice, studies what other good batters do, takes advice from coaches, some will likely study sports science literature themselves (rather than relying on coaches doing that for them). Batters will always want to think of ways to improve their mechanics, and will always want an "edge" over pitchers, and pitchers vary in their techniques. The great hitters from decades ago did not have access to video footage of themselves, their rivals, and opposing pitchers, for example. So while some of them were exceptionally skilled at hitting baseballs (and not just home runs) (and also running bases and being competent in field positions usually) they were not really experts for want of a body of rigorous literature. Conversely, one can of course have sub-major-league skills but enormous expertise -- there are batting coaches and sports science academics after all, and even popular analysts. And sports skills decay with age. Nobel-prize-winning scientists can get senile dementia too; sadly that not just wrecks their skills, it also wrecks their expertise as they forget much of what they've read and studied.