People are listening cos of the credentials of the coaches. For example in ABBH Chad says that big arms come from compound exercises and that he purposly left out direct arm work. It is probably be taken out of context and his perspective is from building a strong foundation, but the guy has like 4 university degrees and trains elite athletes and special forces so people (like me) listen.
There are other factors to consider; if one muscle group (eg back)is way stronger then it will overpower the other (biceps), also the ROM, form, limb length etc will affect which muscles get most worked. If youre rowing and concentrating on using your back then its your back that will get the benefit but its equally possible to row the same weight using your biceps as the main driving force.
For me, chin ups are enough for biceps and I think of them as a mainly bicep exercise and pressing movements are giving me steady tricep growth. However Im just aiming to add overall mass and I agree that well shaped arms grown to full potential do need iso work.
Just my opinion, aint disrespectin ya Prof, dont Hulk out on me!!