In this case it doesn't even matter about whether "directing" is legal or not. Callahan is obviously turning and stopping in order to avoid running headlong into the net, and that's what you have to do with your skates to make that quick turn. It doesn't even hit his skate, it hits him up high on the shin. It's an obviously good goal, which is why it was called as such.
To be honest I think he tried to create more surface area for the puck to hit and direct into the net while not using a kicking motion. I think his intent was to get the puck in the net, and he accomplished that while keeping it legal.