One can say, with absolute and unwavering certainty based on what we know about practice, that folks who spend every waking hour thinking about and learning about some specific skill will tend to display a higher level of competence than those who don't.

Obviously there will be folks who practice incorrectly, and there will be folks who hit a skill ceiling, and there will be a myriad of folks who aren't maximally benefitting from their practice for one reason or another, but if you take a group of people who study and pit them against a group of people who do not study, the group who studies will be more proficient at the given task.