The 10k hours number is also dubious. It just happens to be the average number of hours students at some special violin school have spent in solitaire practice by the time they turn 18 (or what ever age they apply for the school).

Another missing point, and this happens frequently also in rigorous treatment-control studies, is the heterogeneity of responses to treatment. Say, 10k hours might be the average deliberate practice time needed to reach "expert level" (not true), but for some it can take 1k hours, for others 15k, for others infinite time (but they can drop off), and so on.

I also read that specific book/chapter where he discusses 10 000 hours, and the implication based on his bill gates and hockey example, were as you said, that it is a necessary condition. And those examples in particular I think point out how having had the time and experience to get ahead of your "cohort" (people of a similar age or time period)

Not necessarily. You can become an expert in your self-defined programming language without putting in 10k hours.

You probably need ~10k hours in programming in general. Just a lot of the skill transfers over in that case.

The feels more like a violinist learning a new song, and in this case one they made up, rather than learning an entirely new skillset.

You can become an expert in cooking a hot dog without 10,000 hours of practice.

Has anyone ever recognize "expert" skill in hot dog cooking? Cooking, certainly, but hot dog cooking?

What does it even mean to be an expert? What are we allowed or not allowed to be an expert in? Who's the judge that sets what fields you can be an expert in? Is there a range of expertise? Do I have to be in the top 10% of people in a field? The top 2%?

The whole idea of being an expert is an arbitrary social designation backed up by hogwash. We think we know what it means but it's really just hand-waving.