The weather is so unpredictable in Chicago that time of year maybe that's part of the reason they bailed on trying to be a "fast" course. No use paying to rabbit a world record 1st half if it might be 78F, sunny, with half the course into a headwind (or possibly 38F and rainy). Berlin, Paris, etc are more predictable.
Hope it's cool, calm, and dry and someone helps Rupp to a fast one. Would like to see what he can do. (Yes, i'm trying my best to ignore all the back and forth about NOP doping, whether it's true or false, in order to try to enjoy it. Ignorance is bliss.)