The problem is that you did not express yourself very well in your first post.
Secondly, your reasoning does not apply at all.
You think, it someone is going to travel to Badwater, or wherever, and run/walk a great bulk of the distance, then that makes it less likely for them to cheat.
But that is wrong on several accounts. First, since PM lives in San Antonio, she has no choice but to travel to the race. She has held her own fake 100 milers at home but they didn't get her near enough attention as finishing Badwater would. I believe the distance traveled to the race probably makes it more likely for her to cheat because she wouldn't want to invest the time and money only to end up with a DNF.
Second, the fact the someone covered, for example, 80% of the race distance doesn't magically allow them to be able to complete the last 20%. Especially if there are cut off times. I think it is entirely reasonable that PM doesn't go into some of these races with an exact cheating plan and even aspires to complete the course legitimately. But as it becomes increasingly obvious to her and Steve that she isn't going to be able to finish, they scheme a way to skip some section of the course via vehicle.
Third, if there was a good way to "finish" Badwater without running or walking at all, I don't doubt that PM would be all over that. Problem is, the less or a race that you legitimately cover, the more likely you are of being exposed.