The trouble is that you seem to be pushing for a 'One True Glorantha' and that doesn't exist outside Greg Stafford's games.
I see your criticism, but I think it is unfounded.
I don't believe anyone in this thread is suggesting that anyone has to run their own games in any specific way. But if we are going to have any sort of meaningful debate about Glorantha, we have to be talking about the "official version", otherwise there is no common ground to discuss. He isn't "pushing for a 'one true Glorantha'", he is assuming the base Glorantha in order to be able to meaningfully say anything, while not denying that any GM can vary anything.
I observe from your comment above
Well that is just one explanation, none of them are fully correct. Mythic answers are always going to be a little ambiguous and missing certain elements of mythic truth.
That you are definitly a mythicist inn Glorantha. Nothing wrong with that, but do remember the difference between Myth and Time. In the period before time, things were very different. Just what was going on back then is a matter of some debate, and beyond this thread, and complicated further by the fact that Heroquests can change what seems to have happened. However, all that ends when Time starts. There is a definite objective history of things that did in fact happen, and it starts at the dawn. That, after all, is what Time IS. So in that sense there is a "One True Glorantha".
Of course, all cultures will put their own spin on events, and no one culture's perception will be complete, but the Battle of Night and Day happened in history, within Time, so it isn't subject to the same sort of reinterpretation as, say Orlanth and the Evil Emperor.