If you want me to be really pedantic, it is not a specification, it is a recommendation.
People treating it as a specification has made everyone scared of veering from its parameters and experimenting with what might be ideal for each individual site.
In theory, an ideal greens mix could be different for each of the 18 greens on one course.
Yes, thank you.
If you read the USGA Greens Section web site carefully they always refer to the greens construction method as a
recommendation, never a specification.
I've met first time golf developers who could not be convinced that a green could function just fine even if it were not exactly to USGA guidelines. (Which truly would be impossible because the recommendation is a series of parameters, not a precise specification.)
It causes a lot of unnecessary anguish and grief and time and expense in places in the world where you can't get sand seived to spec or spaghnum peat moss is not readily available.
What's more, some people don't understand the physical mechanics involved or the difference between a tolerance and a requirement. For example, the USGA say that drainage gravel should have no more than 2% fines, I had one owner refuse a gravel with <1% because it "didn't have enough fines in it".
Stupid people. How do they get so much money?