Eugonadal = testes working fine. They had no hypogonadism so we cannot compare this by any means to people who has hypogonadal state.
If you are suffering from hypogonadism, you won't heal after stopping trt.
TRT and HRT ( Ie. clomid becoming more popular treatment method ) are simply the only currently known treatment methods for mankind.
If hypogonadism is left untreated, one can always pray and hope for the best but telling yourself "well some day it just fixes itself, nps!" but nah, it won't.
It's usual for people to underestimate hypogonadal health issues and think it's ok you just feel crappy but that's kinda it.
To majority of people, it can take years to realize they could even suffer from hypogonadism, and are taking depression meds instead etc.
Bottom line is, don't leave it untreated, there are a lot more health problems than being on trt where one really has really little if anything to worry about IF the protocol is sensible, unfortunately it's often not.
However, example risk of getting prostate cancer through trt is myth and proven wrong unless you had it before.
For people worrying about kids and who suffers from hypogonadism, do sperm count before starting treatment and take appropriate labs.
Learn more about hrt treatments like clomid etc. Expect nothing when trying to conceive a baby. Depending on sperm status, hrt only gives a percentages of hope, not guaranteed success.