Yes this is something that noone of us understand.
What I have found out is that when I am using big intensity , my tissues are becoming a lot harder and I am losing a great amount of max flaccid stretched length.
When this is happening.. I have no growth(did that for like 1 year) and my erect length and girth is smaller cause the tissues are harder and the blood that is entering the dick is not able to expand it fully.. So eventhough my dick becomes 100% hard in the erection the length and girth can not expand fully.I have read people are doing an intense manual stretching session and then they are putting the extender on and they are having longer FSL in the extender cause of the manual stretching that did prior to extending.
In my case its the exact opposite.. When I was doing an intense manual stretching session and then I was putting the extender , during the 1h ext session my FSL was a lot smaller cause my tissues was becoming harder from the manual stretching prior to extending.Its so strainge that every person is so different.
I think blood content in the penile tissue has to do something with it. I also feel the same way like you described after stretching a bloodless penis. It shrinks so bad like a scared little puppy and looks even smaller than before. But when I do the same stretching but this time with some level of semi-erection (15-30%) the session feels better and also the penis afterwards remains somewhat normal.
This is just my theory that I have personally observed during my insignificant PE timeline of 3 months only so it could be something else.
Current: BPEL: '6.7' MSEG: '5'
Goal: BPEL: '7.5' EG: '6'
Started recently with just manual exercises. Always open to discussions and learning from ppl and giving back.