First off, who is the PGA? The US Open is run by the USGA. The PGA of who? Most countries have a Professional Golfers Association; typically it's for teaching professionals and not touring professionals. The PGA of America runs the PGA Championship (which was played back in May at Bethpage Black). The PGA Tour is neither of these and does not set up the US Open, USPGA, The Masters (setup is done by Augusta National GC with some assistance from PGA and European Tour staff but ultimately, ANGC gets final say). The Open Championship is set up and run by the R&A (Royal & Ancient Golf Association, or RANDA).
The problem in previous years is that the USGA has pushed green speeds to the point where balls simply could not stay on the green. Wind kicks up, and the course gets progressively tougher in the late day than it was in the morning, so it's not a level playing field (see Shinnecock last year when the early groups were significantly better than the late groups because by the afternoon the greens were lost).
At Pebble this year, they never got much wind, the sun never came out, so the greens didn't turn lightning fast. Thus, lower scores. The larger issue is that the USGA has, for years, tried to "protect" par as a score and set up a course so that the winning score is close to par. The other majors don't do this, and they don't have the issues that the USGA creates.
30 years ago they should have taken control of the ball. They didn't. If distance is the issue they need to go to a tournament ball (Peter Kessler, formerly of The Golf Channel) has suggested using the 2000 ProV1, which flies about 8-9% shorter than the current version. The other issue is that the USGA tends to ignore the local superintendent. So they use a course once every 9-12 years. The superintendent is there every day of every week and knows that course a million times better than the USGA.