Right. Our Q5 has it and it's pretty slow. I personally don't like it, wish it had been an option. I also bonked myself in the head last week when I washed it, didn't realize it had the under car sensor and was drying the rear bumper and activated it. Stopped it with my head though.
Curious if the aftermarket ones have the pressure sensor? These things open and close with a lot of force, seems like a safety risk without it, and damage to your hatch when opening could be a risk. Our Q5 allows you to set the opening height, in case you have a low garage door.