The key to figures h & j is the effective areas of the different components in this assembly. To quote John Brock (Chapter 4 of Crocker & King's Piping Handbook 5th Ed.) in the caption for figure 46 - "The pressure area of the central portion is twice that of the end portions." The net imbalance area equals zero.

It is unfortunate that the author of your illustration re-used that P*Fcap to identify this effective area of the assembly. Figure h says total effective area is 0; Figure j says total effective area is P*Fcap.