So anyone who fails at professional golf simply doesn't have the right physical makeup?
How about the scores of guys who have made it there before but then can't get back? Did their physical makeup suddenly change and make them unable to make it?
Were Craig Stadler, Lee Trevino, Jim Furyk, or Emerson Darcy overflowing with those magical physical attributes?
Yes, I'd say they are. They aren't quite as tangible as other physical attributes like strength and speed but they certainly exist. I'd image pro golfers would also be measurably better at horse shoes, darts, free throws, basically anything that requires you to repeat the same movement with x amount of precision.
To your second point, I'd also posit that performing at such a high level of skill likely requires everything coming together and is a very 'sensitive' state. I'm not at all surprised that people can fall out of it and not be able to get back.
And finally it's not to say anybody that fails at pro golf doesn't have the right physical make up, there are lots of reasons why someone would fail but clearly there are some things that you need to be exceptional at. I'd say there are some optimal characteristics that lend themselves to golf, interesting example of that, I was prescribed beta blockers for something and found that it drastically helped my golf game, I was steadier over all shots, calmer and was just able to make smoother movement. It just made everything easier. These are of course banned on the PGA (for this reason) but people clearly have varying degrees of natural steadiness so there's a clear advantage there.