Missed. If you are bipedal you have to walk upright. If you are not bipedal, you can only walk upright for short periods of time and you are very clumsy – watch any video with chimps or gorillas walking only sort of upright. Humans can’t knuckle walk because 1) our arms are too short, 2) our spinal cord enters our brain on the underside of our skull, not in the back of the skull, and 3) our pelvis and knees are not straight, but curved. Compare human and chimp skeletons.