Fundamentally, it is all to do with chemical/ physiological reasons - that is the difference between different PE’ers responses and results.
The predisposition to flexibility is chemically driven. Relaxin plays an important part here. For safety, I think it would be OK to re-balance your Relaxin levels, if a blood assay proved you were on the downside. To increase above Normal, is asking for trouble, as you correctly say about increased risk to injuries in pregnant woman. Also the Heart has been shown to be Relaxin receptive.
The “stretchiness theory” is my own marker at the moment in my routine. I, like you, feel I am a hard gainer. However, I am into my 4th week of using my Jes Extender, with daily hours now verging on 12 hrs. I can say I am experiencing a change in the way my penis is stretching, particularily at the final point of resistance when you are up against the resistance of all things, tunica, ligs etc. Is this a pre-condition to a gain? It makes sense when you delve into all the physiological arguments of tissue remodelling. The other marker is after stretching, my penis is hot, as though there is a cellular response going on, perhaps an increase in cellular metabolism in response to stress. If I get a gain, I will feel more convinced that these markers are valid criteria to look out for.
Dermal delivery systems are getting cleverer. Lack of skin irritation for one. Tissue receptiveness is another. However, a tissue under a controlled stress, is going to operate at a higher metabolic rate, thus is more receptive to chemical uptake. Anything left over will only be taken up by the ability of other sites to be receptive to those chemicals, otherwise it will be metabolised by the liver. Here is where the science is; controlled stress through traction, controlled endemic chemical delivery at concentrations in tune with the induced chemical uptake of the tissue. Granted an art, but this is already being done in medical circles, so why not the penis.
Back to your link, he has well covered his ass in this patent application. Kind of “in the event of all eventualities science”. He has definitely created the right arguments, no question - “Essentially, blast your dick with a chemical soup when it’s under stress”. He knows he is sitting on something in this patent application, but it’s messy.
Let’s concentrate on subtle mechanical stress to raise the matabolic rate and thus enabling a subtle chemical uptake environment. Papaverine has been shown to accelerate tissue growth but the tissue was under stress, stress creates receptiveness!