OK, but why 50-50? There's no reason to expect that a priori. It's also better then 55-45 and 20-80, but none of those is good.

I think he was being sarcastic and highlighting the absurdity of the situation.

I think he was implying that better than 50% implies its at least not mostly bullshit, or that we could perhaps draw usful inferrences if we are right at least most of the time. But agreed, none are particularly enthusing.