Several aspect have come to pass over the history of GCA. In the beginning, it appears that it was more of a hobby than a profession. People evolved into being GCA's, they didn't start out with that as a career choice. Since, in the time B.C. (before computers) it could take upto 2,000 manhours to draft and revise construction plans. Plus, those 'drafters' came mostly from the LA schools direct, without spending any actual time as a construction guy. Labor unions precluded someone from just 'hopping ona dozer' - even if he owned it. So you ended up with a couple of generations of soft-handed college boys. Granted, there are some who have had the right situations where they actually got enough 'stick time' to figure out how to shape and finish golf course features - but they would be the exception and not the rule.
Now, with somewhat less rigid contracting practices and more 'design/build' arrangements, there may appear to be less of a division between architect and builder. But, this only holds true for those who do one or two projects at a time (can't be everywhere at once).
Now that we are in an era where drafting is a forgotten art, guys can hop of the computer and on a dozer all day long (since the laptop brings the office to the field). So, if anything, I think there is evolving a generation of GCA's wityh a much wider and deeper skill set. This can help in the design process because now they know how easy or difficult something is to build, they can adjust their designs accordingly.