Could you please explain how the ratings were done for the 27 hole courses at the Worlds? A conversion factor of three points per shot seems ridiculously low, and compresses everyone towards the middle of the distribution. If you compare the GM scores for round 4 (27 holes at DeLa) and the semi-finals (18 holes at DeLa), you will see a dramatic difference in ratings as you move away from par. Scores near even (par 3) have about the same ratings (1014 vs 1008), but things change dramatically as you move away from par due to the wildly different conversion factors (3 pts per shot vs 9 pts per shot).
This is related to an old complaint of mine, namely that the use of a single conversion factor (3-10 points per stroke) does not make sense as you move further away from average. My guess is that the linear approximation breaks down as you move away from par. Maybe a similar thing happens as you go from 18 to 27 holes.
Based on my experiences this week, there is a tremendous difference between 18 and 27 hole rounds, due primarily to the difficulty of maintaining focus over the course of a 5-6 hour round. These types of properties are difficult to capture in an equation, especially a linear one that has a fixed points per shot conversion.