[thejohnconway]

I guess the question is: would these people be significantly better at any of these fields, if they specialised more? That seems like an open question to me.

My personal experience as a jack-of-all-trades is that if I try to specialise, I dry up creatively and get less effective.

[RBerenguel]

I recently found out about the concept of “scanner personality”, which covers what you mention (I’m also a “sufferer” of it). If I specialise (too much) I feel constrained and dry up creatively as well.

[amelius]

The trick might be to always imagine multiple angles along which you can approach a problem, however specialized the problem might be. That way, you never feel "constrained".

[z3t4]

Many world class athletes are also very good at other classes or sports. But by specialising in one event, it will be enough to take them from just outside an OS final in multiple events - to inside an OS final in one event. This can be the difference between a 1 million sponsor contract or no contract.