Well yes, but just because the UI is finished last it doesnt have to mean it's a bad UI. And as stated above, it's hard to completely finalize a UI when the rest of the game and all its features isn't completed yet. And lets to forget that stuff can be removed from the game as well before final release, not just added.
Though this whole approach to UI design changes a bit when you release a game for early access and you need to present a more functional UI to the public early on in development. But most of it still holds true.