Even the best local amateurs wouldn't break 90 on that golf course the way they had it set up.
Donald Ross on steroids is what that golf course is, and we'll be seeing more of it in the coming years (both in the tour rotation and as a host for either a US Open or more likely a PGA Championship).
Ok, it makes sense that the course is harder.
There's a huge difference between playing for yourself with some buds and having a gallery of thousands, plus television coverage, plus several million dollars hinging on a swing.
The golf course designer told me that the biggest challenge in designing a course is to make it so a pro won't shoot fifty and an amateur golfer won't shoot over a hundred. According to him, the difference between pros and amateurs is much larger than it used to be. Statistically, a good amateur will drive 70 yards less than a pro, and a pro will sink a putt from three times the distance that the amateur will.