This smells like a bad design decision to me.
Cheap 6-pin power input, cheap heatsink... maybe someone at AMD was trying to cut manufacturing costs, but cut out a little too much. Or maybe it was a miscommunication, with the shipping cards using far more power than expected.
Maybe the review cards were funky. Maybe it was some of each.
Either way, a ton of 3rd party cards will ship with 8 pin connectors on custom PCBs anyway. Hell, it might be like the 6850, where we didn't see any reference cards/PCBs out in the wild.