That's not how retcons work. Retcons don't literally fix gaffes, they're explanations that come after the fact. Dialogue changes between the magazine edition and published volume aren't changes to the story.
Luffy later mentions fighting Katakuri as if he was a logia and maybe that confuses you. But remember that he thought the same about Trebol in a similar situation.
ALL living beings have Haki, but there's no way to detect who can use it. When Law asks Luffy, Luffy isn't sure about Law. When Sentomaru sees Luffy use it, he's surprised. Robin likely isn't at a level where it's really dependable. She certainly wouldn't be able to block Diamante, hell Luffy couldn't block Hody. She only hit Monet once when Zoro was already fighting where now she's fighting for herself.
That´s true, it´s just a correction, not a retcon.
Having said that, Kata and Trebol are still different. Trebol was hiding his tiny body under a coat to create the illusion he is a Logia, when in fact he had a physical body that could be touched and behaved as such.
Katakuri literally has a logia like body, he is intangible, can change body shape and so forth, essentially he is a Logia.
But since Logias can only be natural, and mochi is a man made product, it turned out to be Special Paramecia, something we never heard before.