Doesn't that struggle with the sheer speed at which Ishgard forgot that any cooperation was possible? If almost all of society was integrated, this was common knowledge, most ordinary elezen knew friendly dragons, etc., then that makes the later propaganda line very odd. The official position ended up being that there was never any cooperation, and that's a very odd lie to promulgate if cooperation was well-known and spread through the whole of society. If I was a propagandist in that situation, I might prefer the more plausible position that while we did cooperate, the perfidy and inherent treachery of dragonkind led them to attempt to slaughter us all. Our only mistake was believing in their promises of friendship: it was all really just a ruse to gain our trust before they tried to consume us all.

I just don't see why, in that situation, you would try to cover up the fact that society was once integrated. You don't need to do it in order to sell the line that Thordan was a noble and self-sacrificing ruler and that dragons are inherently evil and treacherous beasts. What do you get out of lying to everyone about something that everyone knows, and has clear physical evidence of?

Whereas it feels intuitively more plausible, to me, if even at the time, cooperation was limited. There could very easily be large factions of both dragons and elezen who were skeptical about cooperation (cf. Nidhogg), or who simply had very little contact with the other race. Positing a degree of distrust and ignorance helps to explain how the claim that it was Thordan who first encountered dragons could take hold. If at the time most of Ishgard did not have contact with dragons, save for an adventurous community around Avalonia, I can make more sense of it.

Ah, but I apologise for going off topic. I am, well, deeply skeptical of every version we get of ancient Ishgardian history in Heavensward. The nature and purpose of the constructed history baffles me.

(e.g. EE p. 149: "These founding fathers then chose to join hands with the clergy to establish a new government to rule Ishgard - and to craft a compelling narrative with which they would convince the people to fight in a war against the Dravanians." Um, but firstly, they don't need such a narrative. The Dravanians, led by Nidhogg, have gone berserk and are trying ato exterminate them. Thordan's crime is not widely known, so you don't need a false narrative. The bare facts of the matter - the dragons have gone mad and are trying to kill us all - are sufficient, and in fact, the new constructed narrative doesn't add anything useful to those facts. The constructed narrative is still essentially that the dragons are mad and want to kill us all. Secondly, the founders of Ishgard have no reason apart from self-defense to want to motivate the people to fight the Dravanians. No one in Ishgard benefits from the war. No one gets anything out of it. So we have a situation where the leaders of Ishgard deliberately craft a lie which provides no additional motivation for people to fight a war that they were motivated to fight anyway and from which Ishgard extracts zero actual benefit. Why? Why do anything like that? Sorry for the rant, but I just can't seem to work out any way in which Ishgardian prehistory makes sense. It gets worse if we go back to Shiva or even further. The best I can assume is that every account we have of that history is full of holes.)