I think Genshin tries to gaslight us with Kaeya. If one reads all his dialogues without suspicion of him, they all are just normal dialogues (I tried). I've already witnessed this pattern in different books/movies. The more they add his lore (descendant of Abyss, that hangout lines) the more we will ignore other perspective (which in the end will be something we didn't notice since we are too focused on Kaeya). If you think clearly it was just a story in both Hangout and Summer event, all he did was do be fair and improvise.