I think Demandred's statements in the Prologue aren't that clearly indicative that he didn't know what happened to Asmodean. He says:

But what the DO says is:

This may indicate that the DO know Asmodean's link to him was severed, and even that Lanfear had shielded him. Demandred might have been completely unaware of these facts, and that is what he may be wondering about when he says the DO seemed to know more than him.

Obviously, your interpretation is possible. But I don't think it is the only one, leaving room for RJ's notes to have been from post-LoC as well.

I do wish RJ had dated his notes, or tracked changes.