In specific situations? I get the feeling sometimes (local) government get Google maps to show preferred routes which are not always fastest or shortest for car drivers. Other than that, I've not noticed anything strange.
Discussion
I notice on routes I've done before it will ONLY show back roads despite the main roads being the better option (no i didn't set 'avoid highways'). Or completely ignore the existence of a road and making a 5+ km detour.
And it will guide me off roads I'm already on to take a slower parallel road. It's so weird