I think that reinforces their point if anything. With reflected light, you have a natural, inherent form of auto-brightness because the amount of light coming off the page depends on the amount of light in the room.

Books are not designed to reproduce colors though, and monitors are. If you have aggressive auto-brightness settings, that wouldn't actually make a monitor appear more like a book, it would just make it so the stuff that is actually supposed to look blisteringly white is merely mild. Which, sure, is an improvement for eye strain, but it's more of a workaround than a solution, and since it would muck up color reproduction a lot of users couldn't do this all the time anyways.