Well, I wouldn't subcribe to that explanation. PHM signed for four matches so he was going to miss one tie no matter what; Quimperlé being the weakest team on paper prior to the start of the competition, it made sense to schedule Mathieu for the other ties. The key result for Quimperlé's qualification was IMO their tied score against TC Paris. Had Simon and Paire not blown up their respective very winnable match against Quimperlé, Strasbourg would have qualified even after losing to Quimperlé like they did.
yes, Quimperlé seemed to surprise everybody, including themselves, but it's really bad luck for Strasbourg that they didn't qualify : they had 3 wins and one draw before final round and they really presented a bad team for that final match, with all of their players they really had a team fitting for the final.
I read Quimperlé's captain who said that they were very happy when they saw that Mathieu wouldn't play and that was the moment when they thought they would qualify.