For me it makes sense when you think about philosophers and psychology schools. Lacan didn’t considered himself lacanian, but freudian. To almost quote himself “people ask me if I am lacanian, that I leave that for my followers. I consider myself freudian”. It is a dynamic of who you followed built their own material with other people material, so having a not christian Christ is not the same as having Christ not believing in himself, but considering the path he went through to build his teachings.