That makes sense....but other than that I don't even know what to think
If I jump on the horse normally, I am in the correct position, and mounted to slot 0 (horse.getMountedObject(0) returns my player, while any other slot is empty)
If I manually call mountObject to mount to slot 0, I am mounted on the side of the horse, yet I am able to control the horses movement normally.
If I do the same, but mount to slot 2, I am mounted in the correct position, but I am unable to control the horses movement.