Also, the original To Be Continued was created on the fly because the producers hadn't done their research and scheduled a NEL during a 'take all your money as a penalty' season in a country where it was illegal for the last Racers to turn around and beg in the streets for cab money to get to the airport.
They can't adjust the Book in order to favor a team they think will be popular. But they've got a lot more leeway in terms of adjusting on the fly than a show filmed on a nice controlled sound stage because Stuff Happens, and they've got a history of adjusting things if a Racer is impacted by an error caused by Production, even if they don't announce time credits like they used to. They also omitted a Speed Bump that Vicki & Nick should have faced a few seasons ago because of some sort of snafu during what seemed to be an impossibly hard music task in, IIRC, Russia.http://www.realitytvworld.com/news/the-amazing-race-leg-omitted-speed-bump-due-production-issues-11697.php
(There's some speculation that the production issue as bad enough that Vicki & Nick's non-elimination was unplanned, but production claimed it was a scheduled NEL.)
And I'm sure that production has also regularly thrown up hours of operation signs on the fly in order to prevent teams from ending up spread over three different continents. Again with the TARAS where Charla and Mirna got a day ahead of everyone in Africa because of the Great School Holidays and Hadj mess, went to take their boat to the next task, and instead came across a sign saying the boat couldn't operate that day due to high seas that looked a good 3-5 inches of fierce waves.