I don't know, I feel like you can't really argue Mathieu should have sprinted when their number 1 sprinter was right there. Just don't think he would have had a better chance to beat Pedersen today. I'd rather question if he maybe should have attacked on the final climb, but then again that would have killed their sprinter so I really can't fault them for their tactics.
To be honest, I think he will struggle to win a stage. Yeah there are those two breakaway stages next week, but those kind of stages are extremely tricky to win, especially if you are the best sprinter out of the break and nobody wants to drag you to the finish. It simply turns out that winning Tour stages is extremely hard for classics specialists, especially if there are no Mur de Bretagne like finishes. There is a reason someone like Philippe Gilbert only ever won one TdF stage.