You could just have a speed bump set up for every single leg just in case. Anyway, just because they say predetermined doesn't mean they are. Teams the producers think the audience will root for get disproportionately saved, no question.
I'm questioning it. Just because you say that doesn't make it true. One of the best seasons, season 5, had a long dramatic pause when charla and mirna finished last (because they were popular), and then phil eliminated them. And the non-elim was the next leg and saved stupid twins kami and karli. And noone cared. The non-elim saved Eric and Danielle in All-Stars. Yaaaaaaaaaaay *rolleyes* The Cowboys are one of the most popular teams ever, why didn't Phil pull a non-elim out of his ass for them in Unfinished Business? It seems predetermined to me.
Also, Josh and Brent last season were hardly popular lol.
AND to further disprove your conspiracy theory, in the first few seasons the language of the clue let the teams know a non-elim was coming, because it said "may be eliminated" instead of "will". They changed this in later seasons so it always says "may". The teams would lazily saunter to the pit stop at times, such as when the eventual season 2 winners just walked to the mat, not caring if they were last even though they were with another team because the non-elim was predetermined. From a recap: "Tara interviews that the other clues they've gotten for the pit stops have said that the last team to arrive would be eliminated, and this one didn't, so she was pretty sure it wasn't an elimination leg. As such, she decided that they could just saunter up and let Boston get to the mat first, because Boston had basically waited for them all day. Instead, Wil steps up and onto the mat ahead of Boston, apparently because Wil is under the impression that this is some kind of race."