[kylescheele]

Agreed.

I think this is where you get into mastery vs. experience. 10k hours of a task does not make you an expert unless you've spent those 10k hours deliberately attempting to gain expertise.

This is also where you get into good practice vs. bad practice. i.e., the average golf enthusiast "practices" by going to the driving range, because it's easy and fun and he's probably already decent at using a driver. Someone who wants to become a golf professional practices by hitting a hundred balls out of a sand trap or driving into the wind or any number of other difficult techniques they're not good at yet.

It's not so much the passage of time (10k hours) that matters, as it is how you spend those hours.

To your second point, "mastery" is sort of a vague term. I like your idea of "enough to achieve a certain goal". That's probably better from a mental health perspective too (experts in many fields are pretty crazy because they've devoted themselves exclusively to this one narrow area for years and years).