It may be due to several different factors. Mainly e2/TT ratio
I have guys with total T of 190 and can pop boners any time of the day or night better then guys on 1000 TT. People are playing too many number games. Do I agree that number is too low, Yes but they can function perfectly fine other wise, so low T in these cases are not libido issues but may lead to other issues with cardio vascular, diabetes and other issues associated with low T later on in life. I think its all depends upon genetics as every one set point is different. Some people set point are at 350-400 other are at 600-800. I am finding its really a crap shot and dealing with other issues outside hormones in younger guys helps resolves issues majority of times.