[EdZ]

Since the left is bent at Adjusted Address, does this suggest that ideally, an early move in Start Up would be to flatten it? Gives me a better understanding of the 12-3-0 checklist Section 4/5-- step 16 "Start Up--L/R Wrist Conditions." Of course, there is the option of starting at Fix. Would an early flattening of the left wrist be an indicator that the right elbow is moving correctly?

A qualified "maybe". If the other components, specifically the hip action/motion and plane line tracing, are correct, then you are more likely on track, however it is entirely possible to have the wrists move properly, but be off your plane line tracing.