The only thing problematic right now is how the change of talent gets displayed/reported. It is instantly, which obviously is not the way it works in real life.
Apart from that, I see no problems at all, and the reason is simple: No one knows how talent works in real life... I mean, who knows, maybe Sandy Koufax was taught his curveball by a teammate when he was young. Maybe if he hadn't met him, he would have not developed into the great pitcher he was. So, his talent increased over night
Or maybe if some coach would have been able to teach Shawn Abner a better approach, he'd be leading active players in HR now... who knows? Maybe that's what happened to Piazza...
That's how I view the development engine in OOTP. It does produce good results, and how it gets there is a matter of my imagination.