"Alternatively, your choice of domain could simply be a matter of personal preference, the aspect of the deity that appeals to you most."
This implies that you can select the aspect of the deity that the deity in fact possesses. Apollo, following the Player Handbook metaphor, was a Healing and Sun deity, hence it can provide those domains (He was a lot of other things, like Art, Culture and even in some cases Plague deity but that is besides the point). But this is EA, we have only three Domains available so I imagine those three domains will be stretched thin to cover all the patron gods.
This.
