For VdP the problem is basically we have no indication on a terrain like that. I'm also more inclined to compare him to Sagan than Gilbert. Sagan finished FW once and got 12th.Many people didn’t think Gilbert could win FW either, until he did. I’d be careful with absolute statements like “it’s never happening” when it comes to Mathieu.
Mind you I’m not claiming the opposite either, I’ll just wait and see what else he pulls out of his bag of tricks.
The main problem with such races for dudes like Sagan and VdP is that it's so steep all the way to the line. That's where those stages Sagan won in TA are really different, where he dangles on at his absolute minute, gets a tiny rest, then can win the sprint on a 5% gradient.
It's also not to say VdP is a slouch on those climbs if he doesn't win. These are the best of the world on steep 3 minute climbs, and it's basically the benefit of punch/anaerobic power falls off extremely quickly,