This is true of so many things. Improvement is proportional to the amount of deliberate, conscious practice, which is more uncomfortable than “game time”.
When I used to play chess, I always found short time controls the most fun, but the least useful for long term improvement.
Now that I'm finally playing again, I feel like I'm back to my previous levels, or even better, after just 3 months of playing 1x week.
Having said that, there's also the 10,000 hours thing.
only... Deep sigh!
The closest we've done is just "more game time". The closest we've found is when learning a new tech doing a small project. But that is learning a tech and distinctly different from "practicing" the craft of programming.
I was wise enough at the early age of 12 or so to realize that whatever that "commitment" gene was, I didn't have it, so I kept piano a personal passion rather than try to go to school for it like my parents wanted.
But it still surprises me about the amount of effort to master the instrument.
Commenting as I have heard of fellow musicians sometimes performing almost ritualistic steps or 'cargo cult' emulations of 'famous' musicians to try and replicate their success.
My interpretation is even though I love those practices, I would still make myself tired from playing and concentrating for too long - after that my standard is downgrading. If I continue, I get used to those lower standards more than I could gain expertise.
Of course like with sports the fun thing is playing a game, not practicing for it, so that's what ends up happening.
The thing is with most computer games (I suppose games in general) is that you not only have to learn the rules of the game to get better, you must also study and practice the current best strategies to even stand a chance.