Interesting I might have to look and see if this is the case with the 980Ti's as well.
To be honest I think the "OC" mode in the software should be a higher clock speed than the "Gaming" mode, as when your gaming you want your card(s) to be stable.
I do not think though that review samples should be sent out running faster than what a retail card will, as that is making them seem better than they are for the general public.