Myth no. 1: card is overclocked with PCIe bus: busted. Why? Because I tried taking the PCIe bus up to 125MHz, and the difference between 100MHz and 125MHz... stays the same. Rivatuner, GPU-Z, and any other possible program just report the card's clocks at their stock speeds: 675/900.
Myth no. 2: driver is reporting wrong clocks: I don't know about this one... but if they are then these cards can clock way higher than 750MHz core and 2200MHz mem with just the stock card... and no volt mod?