Realizing there is two modes of tournament green speed, I'll call slow and regular. I generally use the following rule of thumb. Non-Legend RG's tournament slow the other regular tournament speed. But today I was playing Congressional F-18, and I pick tournament slow to begin with. When you have 15 foot putt uphill or downhill green speed makes a big difference and my putts were right on the money. However, on the back 9 I noticed a major difference especially on the 11th hole. The pace of the putt was extremely fast and I was lucky to hit the hole and only go 2 ft by. The next putt was similar and decided to putt the remaining holes as regular tournament. You know when you make the right choice especially on a downhill putt from 15 ft.
I also sent in a bug report, reporting the condition. Needless to say green speeds should be fairly consistent throughout the round and not going from one green speed to another mid-round.