4.1.035 If a rider exits the course for any reason, he/she must return to the course at the same point from which he/she exited. If the president of the commissaires panel deems that the rider gained advantage, the rider is disqualified (DSQ).
It a shockingly badly written rule, but there you go.
As I understand it at Windham 2012 Rach took a couple of feet off the course, but the panel deemed she’d gained no advantage hence the win. I dunno if Gwin was deemed to have gained an advantage in his quali run, but TBH if he’d have pushed back up, he probably would’ve still started form where he did on Sunday anyway.