[rXpX]

As I understand it, briefly:

The point of the cosmology in the Nikayas is to show how the extant Vedic cosmology is affected by the reworking of the term "kamma". The heavily ritualized atmosphere of brahmin sacrifice was built on an understanding of ritual action (karma) within a particular cosmological environment. More importantly, a particular soteriological environment was thoroughly integrated into this cosmology such that a change in the definition of kamma was a blow to the entire structure.

Therefore, in any discourse where a cosmology is being discussed, it is being directed at that structure of the audience's view in order to ethicize it. I think it's very likely that this worldview, and the ritualized aspects of its soteriology in particular, are at least part of what is referred to by "the fetter of clinging to rites and rituals".

I think making a case for an ethic which is inherent in the world is the point, but when 'the world' is understood from the perspective of the Suttas there is no need to rework any particular cosmology in order to account for kamma = intention. If the Buddha's peers had understood another sort of cosmology, for example Norse, I feel he would still have taught intention as the foundation of ethics (per the Dhamma) yet draw on altogether different contextual examples.

Thus, that intention matters in the grand scheme of things is the point, rather than any particular view about the details of one or another grand scheme.