His theory is honestly pretty convincing, especially with the two headed Akatosh motif being what it is. Forget the amulet of kings, the story of Alessia being chosen by Akatosh simply doesn't make sense unless it wasn't really Time doing it.

Two concepts broadly accepted by the community are mythopoeia (as in widespread belief in some aspect of the divine can manifest it into reality) and that the gods are not bound by linear time (and therefore mythopoeic gods can influence events before they were manifested by linear-bound mortals).

However, even with those concepts, for Akatosh to be manifested by widespread Alessian belief in him, there had to be an Akatoshless version of the timeline where Alessia created the imperial pantheon as described in the lore sources. So even if the Akatosh of the current timeline did everything he's credited with, there has to be a timeline out there where it was a different god, presumably Shezarr, for Akatosh to exist in the first place.