This was the example my OSO gave, I'm not sure if this was purely hypothetical or if this happens occasionally:
candidates are doing a long O course, candidate is running and can see neither the Sgt Ins nor any of the other candidates, candidate cheats on an obstacle, sgt ins peeks around a corner and sees this happen, sgt ins asks candidate if he finished the obstacle, candidate says yes, candidate gets kicked out on an integrity violation.
As for practicing humps, you should come up to the North Cascades (in WA, where I'm from originally) and do a few 10-mile off-trail trips by following the contours on a USGS 7.5 minute quad. That will get you ready for anything. Or take a NOLS course, where they'll make you do that kind of thing anyway.
"Peace on earth to men of goodwill. All others stand by."