Yeah i see what you mean. Pros all end up the follow through in the same position woth the upper arm horizontal pointing forward and lower arm almost vertical above that.
Unfortunately the tables are public tables with some errors and machine can't shoot faster. I could make it shoot lower by angling it with a wedge though
1. The robot should not shoot lower, it should shoot higher. You want the ball to bounce. It is better to practice strokes in the beginning with slower high balls than to practice with skidding low balls. You want the ball to bounce then you hit it.
2. Don't try to copy the pros in abstract, post a video you doing a flat hit and then we can tell you what to do to get to a topspin. "Trying to hit like a pro does" without placing it in the context of how you generally hit the ball is the source of a lot of trouble. The pros stay extremely low and lean forward. Mere mortals do not need to finish so high most of the time because they don't lean as far forward.