From what I understood we could approximate the front fiew of a sliced shaft (no glans) as an ellipse, I don’t really see it from the side, unless, as you said, we jelq. While pumping it isn’t squeezed at the base so as to look as an ellipse.
If I take this ellipse idea while looking at this sliced front view of the shaft , it implies jelqing and squeezes do stress the tunica and force it to grow in circumference. Of course this makes sense.
If I accept your view of an ellipse from the side, you’re saying when I make the penis wider, and the penis is as long as before, the perimeter will be more important . When the width stays the same and the perimeter increases, then necessarily the length has increased too. All of this is, if I may say, quite obvious.
But I don’t see how it prevents me from saying my pen was stretched longitudinally (so longitudinal fibers are lengthened) while pumping. As my example of stretching flaccid and straight out is, I think, quite similar.