Judy once taught Conan Gay, that is, the episodes where Judy just appeared, but that was purely because Uncle 73 wanted us to think that Judy was organized in black, and then he kept calling him a boy.

So is James. The author tried to mislead us.

But Belmore knew that he was Kudou Shinichi, so he called him Guy. But it should be noted that Blanche didn't know that Conan was Guy, only that he was an unusual child, but he didn't know exactly that he was a high school student.