Yamato was casual
She didn't keep up
Yamato didnt take her seriously . Yamato didn't even hype ulti as she hyped Luffy.
That should tell u everything
I thought words and phrases like "casual and didn't take seriously" do not exist in your dictionary given how much you refuse to accept these as valid when it comes to the characters you argue against. Yamato only ever looked away once in the clash to respond to Luffy so I don't how serious she was the fight but she looked as casual against Ulti as she was against Luffy and this is base Ulti fighting in Yamato's field of expertise after being blindsided by Yamato's
Thunder Bagua. Why would Yamato hype up someone who literally lives on the same Island as her out of blue? It's not like just she just met Ulti for her to say things like "Oh you're strong, I didn't know you can fight so well until today."