All golfers arrive at the top of their backswing at different heights. Many more flexible players can turn their shoulders farther and arrive maybe a bit higher. This does not necessarily equate to improvement. In many cases, high arms on the backswing, means at some point the arms did lift independently and disconnect. This may look powerful, but more often leads to problems. An efficient backswing using my method, uses the shoulders to move the arms/club up around the spine. Again, everyone gets to different points along this path and then they're finished. Also, once the shoulders turn as far as they can, the shoulders then turn the hips a little to complete the backswing. With my method, the hips do not turn themselves on the backswing. They're turned via the shoulders winding up. The hips will definitely be use to start the downswing to unwind the body.
One other thing to keep in mind about your comments above. I do have a Straight Arm Drill to help teach my students how to use Large Muscles to move the arms/club, but that is only a drill. In a full swing, the back elbow will bend a little on the backswing (no more than 90°) ... and then on the downswing, the front elbow will bend down after impact, as the back arm straightens out (for most shots). Some advanced shots may have differences with elbows bending or not.
Move Less ... Get Good! DUPLESSISGOLF