In Bud, Not Buddy by Christopher Paul Curtis, what contributes to Bud's belief that Herman Calloway is his father?

Throughout the novel, Bud believes that Herman Calloway is his father because of the flyers that his mother left behind before she died. In Chapter 12, Lefty Lewis drops Bud off at the Log Cabin and Bud finally gets to meet Herman Calloway face to face. When Bud first walks in, he overhears an older gentleman telling a story. Bud immediately mentions that the old man, who happens to be Herman Calloway, had to be his father because he was talking just like him. Bud notices that Herman is telling a lie, or is at least exaggerating, the same way he does. That was all the proof that Bud needed to have for him to know that Herman Calloway was his father. Herman proceeds to tell a story about how a boxer named "Snaggletooth" MacNevin hit him so hard that he decided to quit because it was the sensible thing to do. This comment additionally contributes to Bud's belief that Herman is his father because Bud thought the exact same thing when Teddy Amos was beating him up at the beginning of the novel.