This is interesting...two Tour Champions that don't agree on whether wind speed varies by course. That is, if the wind speed average is 20 mph, the ball will behave the same way (or not) on St. Andrews as Pinehurst. I am just a poor Legend, so don't have much room to argue, but I'll step my foot into it anyway.
I believe two things: WGT displays the wind speed as measured at a given height above the ground. As the ball follows its trajectory (which depends on club, spin, type of ball, how hard the ball was hit, temperature, etc) the wind speed at the ball height will change (being less near the ground and greater the higher it goes). I think that 20mph as measured at St. Andrews is the same as 20mph as measured at Pinehurst. However, the second thing I believe is that WGT takes into account the terrain features of a given hole. So, Pinehurst with its tree lined fairways which block some amount of wind up to the tree height will have a different wind effect than at St. Andrews with it's lack of trees. A rough way to simulate this difference would be to reduce the 20mph wind at Pinehurst to something like 12mph for cross winds, but leaving head and tail winds closer to 20.
I wouldn't say that it's unusual 2 TCs disagree on a matter. Everyone plays at his/her way. However, i wrote ''Usually on the Ocean courses you need to play ''more'' wind''....
So, i have to ask. What Pinehurst has to do with Ocean course? Is it an Ocean course?
I will try to explain some of the factors with an example:
Let's say you play St Andrews and you have a distance 183 yards with 15 mph side wind. Let's say you do your calculations and put your aiming point at 10 yds away from the flag, ok?
Now, we go to execute the shot. What type of shot are you going to play? 6 iron 100% fbs, half back, flat? Or 5 iron at 92%? The distance of the clubs in these 2 situations are the same = 180. Do you believe you gonna have the same result if you hit flat 180 100% power or 92% with 195??
The reason is easy to understand. First of all, the 2 clubs are different, one lighter the other heavier. Secondly, 92% of the 5 iron can be in math 179,2 yds, but does not work this way as you depotentiate your stroke. It's not an analogical type of calculation. But let's say for the shake of the example that it is...
An important (actually the most important thing when you set you aiming point on the approach shot) thing is the trajectory (the curve of the ball after the stroke). In the first case you can have an apex of 115 ft meanwhile on a second example you can have an apex of 90 ft. This is an entirely different shot eventhough math says it's the same distance. The curve of these 2 strokes will be entirely different and you are going to get 2 entirely different results cause you don't ''treat'' the wind with same way.
A ball that stays more up to the air will be affected differently from the wind than another one with lower trajectory. That's why a shot with 3 iron keeps rolling meanwhile a shot with 9 iron stops after a couple of yards.
And to prove you that Ocean wind is different, i will give you a test. Go to St Andrews with face wind (6 oclock)...no matter how much strong it is. Stay at about 130-140 yds and play a flat shot. Then go to PB on the first hole and try to find the same distance and wind condition on the first hole. Repeat exactly the same shot you did at St Andrews and see what happens...