You are right as usual Born, the TPC courses are owned by the PGA tour, they aren't the same thing as the courses that the PGA is played on. I believe they made the deal with the devil back in 90 to 95 as well.
TPC is a great course, I have had the chance to play it 5 times over the years. However it is not very long and can't be stretched out much, that is the type of course that doesn't suit WGT well. Kiawah for example is fairly tame when you play it at 6800 yards, move the tees way to where the Legends play Kiawah from and it is one of the tougher courses. TPC Sawgrass is going to be more like Kiawah from the masters tees. Hole 17 looks tough on TV and in real life, but on WGT it becomes a 133 yards 9 iron that the good players expect to hit inside 10 feet.
Harbour Town is similar, in real golf the small greens and narrow fairways make it tough, in WGT land I can hit a 295 yard drive in the fairway 85% of the time, that makes it a lot less tough than in real golf.