I agree it has to be mountain and hilly sites. A few good players here in DFW claim Fazio greens at Dallas National are very hard to read, and Faz greens usually aren't that tough. I think the hilly site has a lot to do with it, but could be wrong, as he has put a few subtle slopes in there as well. I have mentioned the 5th before, where Trevino complains that a small ridge of 4-5% in the middle of the green can make it virtually impossible to get a chip close to any pin beyond it from where you are, on an otherwise 2% slope green.
I have measured many greens, and in hilly sites, for construction practicality, catching up to grade faster, natural drainage outlets, etc., you almost have to follow the grade, and usually put more slope in it than you normally would.
Visually, a flat green looks like it breaks toward the mountain. Even a green sloping a normal 2-3% in the natural downhill direction may look canted the other way. And, in most cases, the hillier the site, the more the side slope to then natural downhill slope is. I have used my digital level to measure such slopes, and inevitably, what looks like a 2% slope to the right can end up being 6-7%.
So, even when you get the direction right, you usually vastly underestimate the break.