At the end of this video, Rabbi David Bar-Hayim makes the claim that not every Sif in Shulchan Aruch (as it is before us) was written by the Beit Yosef himself (Rabbi Yosef Karo). He says that parts were written by him and other parts were written by one other person if not more than one.
I'm not referring to the fact that in many places the Beit Yosef simply copies the exact words of a particular Rishon. In The video Rabbi Bar-Hayim makes the point that from this we see how "flimsy" a great halachic edifice like that of even the Shulchan Aruch could be (because they weren't written as he is claiming by one individual person as great as the Beit Yosef (I'm assuming that's his intention -- meaning those that contributed were perhaps not on the same "level" as the Beit Yosef.)
Is there a reliable source for this or place where it is discussed?