We learn of Inri early on, during which we are less likely to interpret him as a true religious figure. We don't really lean of the gods and such until later - its really not until TJE where we get the first confirmation that gods are real.
So we are likely primed to believe he's not divine.
Given the actual existence of Gods and the state of the world post-Apocalypse, it seems more likely that he was "real". Either an actual Avatar of one of the gods, or simply one of their chosen. I can't remember what exactly he reinterpreted, but that might give us a clue as to which God or Gods he was a favorite of.
Regarding Ascension, it does seem strange there are 2 areas debated to be the ascension point. That echos of religious/human debates (like whatever Church wanting it to be Our city, not Their city). It actually happening seems as likely as any other God Touched thing in Earwa. They seem to have an awful lot of agency when they want, and something like a Holy White Light lifting a person up into the Heavens and discorporating seems like something the Gods might be interested in - even if it took a joint effort to put on a show. They feed on devotion and belief, and such a feat would definitely make some hardcore believers in the "Divine".