I see no reason why one couldn't combine heavy girth work with length work. It seems that the two should compliment one another. Especially, when you think about the layers of the tunica, and that they tend to go longitudinally and laterally. Even if girth work is only hitting the smooth muscle, shouldn't the increased expansion provide additional stress on the tunica with outward pressures (laterally), while hanging is also providing a downward stretch (longitudinal).
Sometimes I read some of these "theories" and think, many of them don't seem to follow with due diligence. It's just some guy who feels like they've been practicing a technique long enough, and with enough success to qualify themselves as knowledgable. The explanations often don't have the rigor that should be followed if we are going to look at PE through a biological/scientific lens. I understand that its based off empirical evidence, but many times the information seems to be contradictory to my experience and knowledge. However, I seem to be a tough gainer, and my penis seems to happily take whatever training madness I throw at it, so perhaps I'm just an outlier.