Does the monstrous form/image on page 21 not resemble the endocrine system of the human body? To speak of Susano'o's personality and behavior, it's very hormonal (fight and fuck). Personification may not be the best way to describe it but he is definity acts human in a primal and exaggerated way.
Every Amatsu was shown to have a "true form" that embodies a part of the physical body, and just like you pointed out... if we analyze each one we may see that the personalities are tied to that.
Now... is it like that because it is just another layer of the "personification" or... does it mean that at least the Amatsu are the body parts of one single being that is so powerful that its divided parts have developed their own sentience and are all transcendent beings?
Just imagine the implications, Miyazaki's level of concept, and I say this as the highest of praises.