Very True apskip, but there is a very large difference. In season 10 they relied heavily upon two teams Erwin & Godwin and Lynn & Karlynn now if David & Mary hadn't taken the Fast Forward Dustin & Kandice or Erwin & Godwin were keen on going for it.
If they hadn't done it they most likely would have stayed grouped with which ever "Six Pack" team would have let them.
And even taking the last team, that still would have let them complete said tasks and take the 30 minute penalty and still beat two teams at the mat. And since the last team was over 4 hours later before getting (according to interviews) directed (they had never found it using locals or on their own) to the Detour to get the clue to head to the Pit Stop. I think it is very safe to say that it is unlikely that David & Mary would have lost that much time (in fact since they never did find the location of the detour, without production help, Peter & Sarah could have been out there hours upon hours longer).
While it is true that it is mathematically possible that Peter & Sarah would have eventually found in and completed the detour and found the Pit Stop and that David & Mary would have been later, it isn't likely.
Again in 15 cycles no team has ever been as lost (or lost as much time) as Peter & Sarah when being so close to the city they were supposed to be in (at least 8 full hours). It hasn't happened. Hell they lost more time then any team that have been lost when driving across multiple countries. In fact while many teams have gone further off course (Debbie & Bianca, Meredith & Maria and Lake & Michelle as poster children for this), None lost as much time.
And only one other team (and this was over some distance) that I recall ever got directed by production to their destination (first season's Paul & Amie in the desert), though I don't know how much time they in fact had lost.
