How else can their absence be explained? XB360 isn't a good example because we know the heat solution was poorly handled, and since the extra cooler, any absence (unconfirmed?) could be a fixed cooling solution elsewhere in the cooling chain, making up for the prior bodge-job. PS3 didn't have a cooling problem, and was clearly well engineered. I'm guessing those holes were put in as a measured consideration of airflow, and now that's not needed, it points to less heat. Or the holes being moved elsewhere, I guess. As 65nm has been on the cards for ages, including IIRC comments from Sony that 65nm would be rolled out in a SKU that benefits from the cost saving of the shrink, I'd be very surprised if the 40GB isn't on the smaller node.