Originally Posted by rkelley
They actually are swinging up at around 45°.
Here's an analysis of their actual forehands prior contact:
I see the confusion. I would consider it as much more - the angle which the racket face makes with the horizontal. That is the angle "seen" by the ball. The lead-up slope to the ball is not important to the ball.
The angle with the normal can be 10 to 20 degrees, so with the ground, 70 to 80 degrees. You are looking at the swing path of the eventual point of impact.
PS: Perhaps the lead-up slope is important too because that puts the upward force on the ball. Need to think more about it.