One example I can remember is that Willie Mays had a lifetime OBP that was .002 lower than his OBP at age 24, which was odd because Mays had some of his highest OBPs after age 40. I would have expected that his OBP would go up as he aged but it fell a bit. well OBP is gonna factor in batted ball luck. You want to look more at BB%. Mays for his career was 11.7% And most of his seasons were pretty much around there. '71 and '72 saw steep increases though, but perhaps that a late career "stop swinging as much" stance of some sort. But anyway, his "Best" years were '65, '64 '62 and '54, and his BB% there 11.9, 12.3, 11 and 10.3. All pretty much around that 11.7% career mark. Also the elites like May are always going to be outliers. You want to talk about modern guys that have made their OBP/walk rate jump? You want to talk about Starling Marte. Career 5.3 BB%. 2021? 8.2. His BB/K ratio SIGNIFICANTLY better in 2021 than any other year. https://blogs.fangraphs.com/starling-marte-is-not-swinging-like-never-before/https://blogs.fangraphs.com/starling-marte-is-not-swinging-like-never-before/ Some analysis there that suggests that Marte's increase isn't just all smoke and mirrors either. But yeah, for the most part, players don't randomly develop better/different skills. You have a good eye or you don't. The flip side is a guy like Matt Harvey, who has pretty poor control, and once he couldn't fake it with plus velocity, it became very clear he didn't have that additional skill to be elite without it.