I think apart from FP, TSC is using another criteria which is PD.
I have noticed that the majority of the cases which are being approved have a PD of 2000 or older. This is true for those 2002 cases too who are being approved. There are few exceptions but in the tracker PD data is not very accurate as many people dont know it or havnt entered it carefully. PD of 1999/2000 results for people who have gone through a lengthy LC process and hence their total time is very long. Thus it seems to favor EB3 guys at I-485 stage. People who skipped LC (e.g. EB1) have their PD of 2001 or leter and I think they are less likely to be approved soon even if they have had their FP done. I know PD should not matter now as all categories are current but that affects for filing I-485 only, as far as processing by TSC goes, I think PD is also playing some role.
This is also consistent with the known fact that at I-140 stage at TSC, EB3 people are approved much quickly, then folloed by EB2 and then EB1.