I would have to disagree that angle of deflection is not relevant. Imagine a racquet face that is 15 degrees open. Now try to "catapult" topspin with that. Contrarily, with a face that is 15 deg. closed, an upward swing where the strings grab and throw the ball in a initial upward direction if the speed/force of the upward swing are sufficient to overcome the downward angle.
You have lots of angles and forces either working against each other or working togetherto form each type of shot.