… but at the same time the tunica is also being stressed and also stretched…
No it is not. The outer tunica is not being stressed. It is very difficult to provide enough stress to the tunica to fatigue it OTS, SO, and RSDT fulcrum where those stretches are specifically designed to stress the tunica.
If by chance the tunica was also being stressed by the ligs, it would be very minimal, not nearly enough to fatigue and deform it. Without fatigue, no gains.
I still believe that the outer tunica is not affected by BTC and that the Inner tunica is only pulled out, not stretched or stressed.
It is not until we stretch OTS, SO, RSDT fulcrum that we realize gains from stressing the tunica.