Board Thread:Theories and Speculation/@comment-36512555-20200202084241/@comment-9782468-20200204064422

Intimidation is a thing. They all assumed the Itachi in front of them was the real deal, so they proceeded with the utmost caution. Once Kakashi actually engaged him in Taijutsu, he knew something was off.

Kisame has been his partner but he still doesn't know Itachi's abilities like Itachi knows them himself and he doesn't know Jiraiya's abilities like Itachi would.

Literally doesn't matter what Kisame believes, it's about what Itachi believes. And Itachi said he could tie with Jiraiya. Like I said, there was no reason to lie there since he had other things he could have said that were true as well. The only reason Kisame didn't believe him was because he didn't know Jiraiya's abilities well, unlike Itachi.