The fact that the two components of an analogy are not the same thing is the point of the analogy. If they were the same thing, the analogy would be useless.

In this specific analogy, the point is, despite having different business models, society benefits from either conglomerate separating their respective two aforementioned business units.

No, their businesses are managing money and taking companies public. They're overall revenue would benefit from aligning those businesses, but they aren't allowed to. They are kept separate because of the risks of having them together. The Facebook scenario is a different (but comparable) situation.