Now I can understand how the pitch can change from one plane to another, but how does the width of the seat change? Are there really two different domestic F seats that differ only in width??
Believe it...they are different. Seat width can be and is often different from plane to plane in the same class of service. Just the way it's always been. There are reasons. Such as desired aisle width vs. width of plane. Type of junk they cram into the console. Aircraft and seat manufacturers are different. Etc, etc.