I think this article went around a while back. Or at least one like it.
Concerning gains, it is really funny that the Dr. would even mention the internal smooth muscle. This smooth muscle only lines the interior of the vessels within the CC and CS. It actually has nothing to do with gains.
I have seen this other places about the increased pressure swelling the smooth muscle tissues etc. The deal is, these tissues will expand easily. In fact, the tissue is designed to expand. The limiting factor in gains, and what is tough to do is to expand and/or stretch the tunica.
The tunica is the structure which, under pressure, causes an erection. When pressure is raised to above normal, the tunica is what resists, not the internal tissues. The danger from PE girth exercises would come from tearing the tunica. But this would take a pre-existing condition such as peyronies, or an incredible amount of pressure.
I would hope nobody of sound mind would approach these levels of pressure.
The good Dr., it appears, does not understand how the penis works, or the dynamics of increasing internal penis pressure.
Bigger