The Drill is primarily about, getting the arms/club back down in front of the body (using the body's rotation to move the arms/club).
Now, the job of the elbows, are to keep the radius the same length if possible for more consistent results. The back (right) elbow has to bend some on a full backswing, while the front arm is (basically straight)... and the front (left) elbow will bend (down), after impact eventually, while the back (right) arm straightens. I would not practice a straight right arm on the backswing, because it needs to bend at some point. You want to feel the body "WAIT" until the backswing is finished, so the body can then bring the arms/club back down. Many times if someone has problems leaving the arms/club behind it is because, the body did not wait ... or the backswing is out of position or way too long due to a breakdown. If you start with a short "ALL SHOULDERS" backswing... you can easily wait for the shoulders to stop... then use the body and feel the arms/club come back down and around to the left. Keep it short to learn. Don't worry about elbows. Just make sure the arms/hands are not helping on the backswing so they are "submissive".
Move Less ... Get Good! DUPLESSISGOLF