manipulation

Yes.

black arts

I don't think so. It seems about as black as using the pomodoro technique to manipulate your basic impulses.

causation != correlation

Yes, but given the evidence, I'm pretty sure there's a causal relationship in this case.

What about, say, good leaders?

Data point: I have recently improved my leadership skills by spending time with good leaders in a group that considers those traits high status. (Good leaders still made up a (substantial) minority of the group.)

thesis likely literally false, seek metaphorical sense?

Strong agreement. The thesis is explicitly labeled as literally false in the source.

If anything, to become e.g. creative, you'd be better off by meeting people who are currently becoming creative not who are already creative.

I would be really, really, interested to see data on this. My intuition says you'd do best to spend time with a range of people: a little time with masters, a lot of time with people who are somewhat better than you but whose skills seem within reach, a lot of time with people at your level, and a little time with novices who you can teach.