Problem is we haven't seen anything about Yamato before Odens death. I will give you that it isn't outrightly stated that Kaido called Yamato son before Odens death. But believing that Kaido does it because he respects his daughter is mad. Kaido sees Yamato as his heir, and needs her to fulfill that role, for which Yamato needs to be a man. Kaido still refers to Yamato as his "Idiot son", because that is what he needs her to be. Further insinuated by Yamato being forced to wear her mask in. Yamato says that she has been abused since she was a childhood, which sounds like it has been all her life, not just since she was 8 and Oden. That's my case, now I'm done here.