Can the AHA's newly revised BLS on adults without the use of proper body mechanics for bystanders really achieve a return of spontaneous circulation?

Hope you guys have already red the assessment tool of the newly revised AHA BLS for adults (see attachment in JPEG). The answer is "sometimes yes", if the victim/patient is less than 5 minutes from an unwitnessed or witnessed sudden death. However, should the proper use of body mechanic be emphasised on the assessment tool of the AHA BLS for adults especially the proper use of hands, arms and body to pump the chest?