Yoshi P never makes promises to us, which makes the accusation that he lied all the more hollow. He says things that he wants to do, but he's also quite careful to let people know to temper their expectations even with the things that he says, as not all of them will come to pass. And I've found the vast majority of FF players to understand this. Nothing is a promise. It's all tentative.
But Val's toxicity continues to shine through, so no surprise.
Perhaps you forgot, but at one point they even threatened to stop doing Live Letters because the fan base got their panties in a twist over some minor feature not making it in that was in a live letter. They took the time to make it PERFECTLY CLEAR that live letters are a glimpse into the dev team's current ideas, and that not everything will make it into the game.
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I thought about this too, but I realize where a lot of FF's good writing comes not from its constantly higher stakes, but the strong characters within the story and the moment to moment interactions that makes it feel very human. I think that, despite Zodiark and Hydaelyn both gone, and us having traveled to the edge of the universe, they're still going to knock the story out of the park somehow. Whether the 13th is part of the next expansion or merely just 6.1-6.5 content, it'll all still be wonderful.
Of course some people will be disappointed if there's not a whole expansion about the 13th, because their EXPECTATIONS are already that the next expansion is about the 13th. And if it isn't about the 13th, they'll make nebulous statements about how the expansion was supposed to be about the 13th, but got a rush job, etc. Basically unfounded rumors. Or ones that are only half true.
Like the claims that Endwalker was "supposed" to be two expansions. When in reality, in early development the team was deciding between making it two expansions or keeping it one (since that was the original plan) but ultimately decided to keep it as one expansion.