There are 450 NBA players and 250 golfers on the PGA tour. So if you take this out of a sample of just men in the USA (massive underestimate), then to be a NBA player is about 3 / million and pro golfer is about 2 / million. So that means if there was no correlation, to be both would be 6 / trillion. So if they were correlated such that the combination is 100x more likely than average, the odds would be 0.6 / billion, or 2 men on Earth. But, this doesn't take into account the tradeoff in training time between the 2 sports. Realistically, that would be zero people. So one would expect even with a strong correlation, nobody would be able to be a pro athlete in multiple sports. But wait, some people have! https://en.wikipedia.org/wiki/Deion_Sanders, and your example of Michael Jordan was able to play in the minor leagues of MLB, something that most people could never come close to if they trained for it their whole life. So, yes, there is absolutely a general athleticism.

edit: so would be higher numbers because would have to take into account number of people who have been pro athletes at some point in their life, not just right now. But not enough higher that the point doesn't stand.

Also, Michael Jordan's golf handicap was 1.3, which is not PGA level, but extremely good (top 3% of all gofers). On any given day on a random golf course, good chance he'd be the best golfer there.

I'm not sure that's anything more than an encoding issue. The apparent bifurcation at "above average" is probably reducible to "above average in at least one technical domain" with an additional encoding for "above average in more than one technical domain". Your concern is resolved by the first, with information loss of polyglots captured by the second.

Indeed. And that what these tests were all originally designed to do before they were coopted by the eugenics movement. IQ tests are really good at detecting if someone needs more help. They are not good at detecting if someone is smarter then another.