If you read Dan's blog, you'll see that he has a physical therapist coaching him. His team of advisors have a good plan and it seems to me that avoiding injury is a big part of that plan. For example, Dan currently is not using any big clubs - the largest a chipping wedge. If his spends most of his practice time near the green how is going to injure his shoulders, lower back or knees?
In a recent blog post Dan mentions that his physical therapist will prescribe a certain weight lifting program to strengthen his muscles enough to achieve the driver head speed that his golf coach plans that he should achieve.
I suppose that today's golf pros, those actually on the tour, have each put in those thousands and thousands of hours of practice, regardless of whatever athletic gifts they received at birth. So are injuries the reason most near-pros never make the tour? That would be the case if your point is true. I think that they don't make the tour because it is simply too much effort and dedication to put in all those hours of practice.
And that's the wonderful thing about Dan's challenge. If valid, it means that any of us may achieve outstanding results if we put in the hours required to gain the expertise. Golf, in this regard, is a model for any skill we need to satisfy our aspirations.