"The Churn," the official podcast of the show (it's a little more wacky that RDM's on-line insta-commentaries for BSG,* but they always have at least one writer on, so it scratches the same itch) has talked about about how Errinwright's role has been expanded in the show both because they like the actor, and since the show has a less rigid point-of-view conceit than the books (I gather, I haven't read them), they have the option to spend more time outside of their viewpoint characters and show stuff that was only happening implicitly at the UN or wherever in the books.
*Excepting the ones where his wife was on and they spent half the episode busting each others' chops. Those are equally as wacky as The Churn.