I think 99.99% or 1 in 1000 for 8" is for bone pressed, nbp is more rare as its combination of bigger penis than 8"bp and not much fat pad or bigger fat pad but monster penis.
For PE I think jelqing and manual exercises is the safest way to get bigger, risk of permanent damage or injury is relatively small. I personaly didn't see any side efects from jelqing only positives like harder erestion, more intense orgasm, almost imidiately increase in erect lenght because of erection quality improvment to the max, I even felt pain after erection caused by rock hard erection.
I stoped PE though cause I had no time, right now I have time but Im too lazy to start but I will.
The most dangerous is imo penis extender cause can more easy damage penis by restricted blood flow above glans - the most sensitive part of penis.
Manual PE is safe if
1.You have good regeneration, sleep, and healthly lifestyle, nutrition, minerals and vitamin balance etc.
2. Jelq wet without erection during start and maintain floppy low erection level during whole sesion
3. Don't grip to tight and not slide on glans, do slow moves 3-5 jelq, stop before, avoid pain, dont do PE right after sex or masturbation wait few hours
4. Monitor how you feel and react quick to situation