As far as I can tell his opinion just differs from yours, and to an extent I would agree in that I trust that the guy who just won coach of the year and lead Laval to 1st in the league knows how to do his job.
But the 'facts' aren't only on your side of the argument either, Primeau going 21-2-2 with a 1.96 GAA and .927% is also a fact. Despite his extreme talent and great first few games, Fowler is still a rookie pro and that's a fact.
It's not shocking in the slightest that Vincent went back to Primeau for game 1 regardless of what Fowler did. I watched game 3 versus Rochester and Primeau was not great, but Laval was also terrible and completely flat. I assume he went back to Primeau because he wanted to give him the chance to bounce back, and because he has played and beat Rochester multiple times this year. He didn't prove he deserves to start over Fowler in game 2, and now he's not as Vincent has gone back to Fowler.
I think you're making a mountain out of a molehill over this personally, and I have no objections with any of Vincent's decisions so far.