Some other set of starting assumptions could be slotted in there by somebody else and a different theory would result. At least I am telling you what I believe before the theory starts. These claims all derive from the starting assumptions. Arguments about cultural relativism are readily addressed as choices about starting assumptions. This approach does not beat the conundrum of cultural relativism.
Any theory is semiotic, a system of meanings, and meanings come from cultures.
The goal of Generative Realism is not to say what is True with a capital T, but to extend the standard conceptualization of mind and reality held in my culture, while holding the cultural arbitrariness to as small a conceptual space as possible. I think so. We have history, or rather, multiple histories, for that very purpose. All history is just somebody's interpretation of what happened. But there are lots of different interpretations.