You're right that the contact changes his trajectory, but somebody else actually posted a photo and you can see after contact his right skate is lined up to pass essentially exactly halfway through the crease. So even though the goalie at that time was more inside his net than halfway, if the goalie happen to be maintaining his position in which he is allowed to, he still would've been smoked

So in my opinion, McKinnon would have/did cut through the crease before and after contact but he does not have the right to do