The part that does the work
Two decisions carry the whole thing
The two agents are separate on purpose. One decides what is worth saying, to whom, and why now. It never writes a word. The other writes. If a single pass did both, it would pick angles that are easy to write rather than angles worth saying, and you would get competent posts about nothing in particular.
The reviewer never saw the draft being written. It is a separate call with no drafting context, so it has nothing invested. A model asked to critique its own fresh output grades generously. One handed a finished post and a list of rules does not, which is why it can score a post six and send it back.