S2 and S4 were because of the Fast Forwards. This is something that's what I like with different winners. Makes the race unpredictable. Ever since the Fast Forward was reduced, I think TAR 7, TAR 10, TAR 11, TAR 14 and TAR 16 are the ones with the most winners, with 6 teams winning 1st place throughout the race. No other seasons have gone beyond 7 or 9 winners like TAR 2 or TAR 4.
And not to forget that the first Leg of TAR 4 permitted 3 teams to win the leg, that is.. Amanda and Chris, Steve and Josh and Millie and Chuck. But Steve and Josh and Millie and Chuck each won a leg with the Fast Forward on another time other than the first leg, so it doesn't matter because it's still 9 different teams winning on different legs. The only 3 teams who didn't taste victory that season was Debra and Steve, Russell and Cindy and Monica and Sheree (nearly tasted victory if Steve and Josh didn't take the Fast Forward)
It's not some kind of a pattern, but it's interesting to see that after the reduction of the Fast Forward... no other season had managed to get more than 6 winners but we do have many stuck with 6 winners (5 seasons I think, if my calculation is not wrong)