Had been. They've been consistently improving since their Speed Bump. Yes, they slipped in the previous leg, but overall they're doing much better than the first 3 legs would have indicated.
That was what the U-Turn conference in the previous leg was all about. The teams there "agreed" that there were two valid targets for the U-Turn. Nic and Vic were on the list due to their consistency and performance prior to that discussion. But the primary target was Colin and Christie. Becca said they were on a whole other level than everyone else, and she's right. Nic and Vic had been incredibly consistent (mostly in the top 3), but Colin and Christie not only hadn't (and still haven't) been outside of the top 4 all Race, they'd also won a leg (whereas Nic and Vic hadn't). And note that the teams involved in that conversation did all target the bigger threat.
In regards to the U-Turn Vote itself; you can't blame TPTB for inventing it. It was originally invented in the Israeli version of TAR, HaMerotz LaMillion. Starting in their second season, they had a U-Turn (or Yield) Vote in the first 9 of 13 legs. The vote was at the start of each leg, and there was no abstaining (it was even called the Must Vote U-Turn/Yield). Typically only the one team with the most votes got affected, but in the case of ties, all tied teams were affected. This concept was also used in TARChina, TARAustralia, and TARPhilippines before it got here to the mothership. (And I think they only decided to try it here due to the crossover theme...at least, I hope that was the only reason.)
Be glad we didn't get the second version of the U-Turn Vote that the Israelis had in their 3rd season. It was a cross between the Vote and the Double U-Turn. Same voting rules applied, and the team with the most votes got U-Turned. But that team also got to force one other team into the U-Turn.