Those split frontal profiles, F-35-versus-others: First, the eye perceives dimensions better than area. Second, we're all used to seeing front views so we have a symmetry bias. (The attached is rough and ready, but doesn't tell quite the same story, does it?) Third, 2-D views of 3-D objects don't tell the full story by a long chalk.
Code One front and side aspect comparisons are helpful.
Note particularly, in the side profile, how the body upper and lower mold lines diverge vertically behind the inlets on the F-35, to a much greater degree than on the X-35. In the front profile, it is clear that the resulting greater depth is sustained across the width of the airplane. If we define "fatter" as "having a greater cross section relative to length" the case is closed.
Now, whether one likes the muscular look or not is a personal matter...
https://www.youtube.com/watch?v=FVY0Hy-D7XE
...but does the airflow at Mach 1 share your opinion?
Now, if anyone can produce evidence that you could have put 2 x 2k bombs in the X-35 OML, I'm all ears.
Of course that isn't conclusive. The CDAs were there to demonstrate traceability to the PWSC, and there were no rules that said that they had to look the same. The assessment criterion was whether the CDAs performed as predicted, because that was supposed to give the customer confidence that the design process was sound and that the proposed design could be built.
Pity that it did not work out that way.