I don't claim that seeing four knuckles necessarily leads to no forearm rotation. Sure, golfers can show four knuckles and have any manner of backswing. What I said was that there is no hope of my keeping square along all of the 225 degree arc if I don't show all four knuckles. This requirement, along with the proper placement of my right hand, and the required manner of takeaway, allows my to keep square to the arc.
I don't believe you.
Your 225 degree estimate speaks to that - if the shaft is traveling 225 degrees, your left arm is traveling about 225 degrees too.
The only way for the shaft and your left arm to get out of line would be to rotate the left arm!