The claim comes from Quora.com. One of the answer to the question "How accurate is the portrayal of the Marine Corps boot camp in Full Metal Jacket?" reads as follows:
Full Metal Jacket opened in the United States on June 26, 1987. A Marine four-star named Alfred M. Gray, Jr., was in attendance.
Six days later, General Gray was installed as the 29th Commandant of the Marine Corps. (General Gray is the only Commandant to wear the Utility Uniform in his official portrait.) One of the first things he did was to investigate the boot camps at Parris Island and San Diego to see if they were really as brutal as the one in that movie.
He was not happy to receive the report: “Sir…if anything, they’re worse.”
Large parts of the USMC boot camp Program of Instruction were altered at General Gray’s direction. Under Gen. Gray they created the end-of-course test called The Crucible.
Call Full Metal Jacket a “period piece.” It is what it is, but it’s not what we now have.
Did General Alfred M. Gray, Jr. order to investigate and subsequently alter USMC recruits' training program as a result of the publication of Full Metal Jacket?