I've read the reviews but even the early reviews were using 970's with non reference coolers so there is no comparison to a reference type blower. If the case isn't clearing the heat efficiently and the cards are heating up then that = more noise particularly if other fans in the case are having to speed up to deal with the additional heat in the case.
Also it is incorrect to claim where they are installed makes no difference - an open air cooler will just recirculate the air around it, if there isn't sufficient airflow around the card that's going to cause problems particularly if it's tight against another card also producing a lot of heat.