Just skimmed the whole thread. Where I think it goes wrong is in failing to understand that golf involves a whole collection of athletic and intellectual skillsets, not just eye-hand coordination or fast-twitch muscle fibers. It involves proprioception, visualization, depth perception and angle perception, muscle memory, flexibility, durability. Plus experience with wind, a couple of dozen species of grasses and forbs, conditions of dryness and dampness, and memory for all of this which only comes with years in the sport and playing different courses under different conditions. Is golf the most complex game ever? Surely it is. The only thing that limits its complexity is that the ball is at rest when struck -- fortunately for most of us!
And as the thread seems to be heading, discussion of "freakhood" comes down to theories of nature versus nurture. Some are prejudiced one way or the other. I think there is overlap, so that one who is not genetically gifted can by determination and struggle come close to the summit, or at least, I hope it might be so.
Probably tests could be devised to examine children and adults and calculate the relative potential skill level of each. So that, instead of taking our children (or ourselves!) to golf teachers, we would take them first to testers, who would then advise us if we were wasting our time or not, within a specified level of confidence. Same thing with other sports. And the confidence level will never be 100%. Do we really want to do that? If we do not, then all we can do is let matters take their course.
Athleticism, btw, is not one skill. It also is a collection of different skills, and even top athletes in any single sport have their own unique blend of aptitudes. Take pro centers in basketball: they can all jump, move and react quickly while having considerable endurance in their legs, have quick hands, good eye-hand coordination, and they will be tall, but there is a lot of variation anyway. If you had examined their muscle fibers for percentage of slow-twitch versus fast twitch when they were teenagers, the results would probably be all over the map.
Fortunately, some of what used to be regarded as innate aptitudes can be changed. You can develop new neural-muscular connections, multiply your mitochondria, possibly even grow new brain cells and change between Type 1 and Type 2 muscle fibers. So let's not be too quick to judge.
Just because a kid is uncoordinated, totally unsuitable for a sport does not mean the kid cannot and will not change. Teachers and parents must always beware of pigeonholing and being judgmental.
In the past, successful, even famous, pro golfers were not necessarily overall athletes, or even very athletic. If you are an older fan, I'm sure you can make out a list of horribly unathletic professional golfers, some of whom still play in the senior tour.
The game is different now. There is no stigma in being a professional golfer, or in being a college grad who makes a living playing golf. There used to be. And the living is so much more appealing, for the elite few. Snead told stories of the tour in the 1930s, where golfers "rode between tournaments four to a car, and slept two to a bed." No more! [Can you picture John Daly sharing a regular size mattress with Vijay or Tiger, and both playing the next day?]