Based on my knowledge, It all depends how sensitive your hair follicles and body hair follicles are to DHT and other androgens. And I heard other genes except AR gene located on X chromosome determine how your body hair react to certain levels of androgen hormones.
I suppose someone who has low sensitive body hair do not develop hairy chest, legs, back etc, but that same person may develop male pattern baldness because he has sensitive scalp hair. On the other hand, we know there are many bald persons around who have no body hair. They probably have very sensitive scalp hair, and sensitivity of their body hair is much less or they have particularly low levels of DHT which is not enough to turn their vellus body follicles to terminal stage. So, as far as I can understand it all depends on sensitivity of your scalp and body hair.
You can see dozens of examples among celebrities, football players, actors. Vladimir Klicko has no body hair (I don't know if he shaves his body) but I doubt he has low levels of circulating T and DHT. So presence of chest or back hair is maybe not good sign, but only if you have susceptible scalp hair. But very very few of them have problems with hair on abdomen, back or chest. In most individuals chest and back are less sensitive.
So answers to questions:
- Are some people just prone to developing more body hair from the same amount of DHT? (like people having hair on their head more or less susceptible to DHT damage)
Probably yes. We all know there are people who have a lot of body hair and have NW0 hairline. So, I suppose that is clue that sensitivity of body and scalp hair can vary.
- Can someone have body hair that is very receptive to DHT (making it grow), but have follicles on their head that are less receptive to DHT (damage)?
Yes, he can.
Another interesting observation is some males develop hair on chest, but they don't have, even not little, hair on legs, arms or legs. So, distribution of body hair is determined by genetic factor. You first develop body hair on parts of body which are more sensitive or receptice to T and DHT. In most people those areas are legs, arms, pubic and etc. During puberty, males usually get hair on legs before other parts. Legs, arms, pubic, armpit are areas which are more receptive to DHT in the majority of people. And if you look to females, they also develop hair in that areas. As we know a lot of ladies have to shave their legs, some even have hairy arms.