What did you want them to do? Phil had already made a big deal at the starting line about there not being any non-elimination legs. They have the route and destinations all planned out as to what episode will take place where. They have the exact amount of teams to fit the schedule. And then a team becomes unable to continue. At that point, the producers have to make a decision: Do we edit out all the stuff about non-elimination, run this leg as non-elim, and then have it be the only one all season? Or do we just tell everyone up front that Team X can't continue, so since we've already told everyone there will be an elimination for every leg, that counts as the elimination for this leg.
Actually, I guess a third option they could have done is had a short bit at the beginning with the eliminated team explaining to the viewers what happened, and then cut to the race with the rest of the teams have a traditional staggered start so they don't actually know that a team has been eliminated. And then when the last team arrives at the mat, Phil tells them they're the last to arrive, but actually Team X had a positive Covid test and had to be removed from the race, so you're actually still in it!
Did anyone notice that when Phil was doing the video call with the two eliminated racers, and they edited it to look like Phil was talking to both of them at the same time, they were actually sitting in the same place with the same picture in the background from the same angle, so it appears Phil had separate conversations with each of them using the same device, and then they edited it together to make it look like a three-way call.
