Do you have multi-display enabled? When using multiple monitors (or perhaps even having it enabled....I haven't tested either way), the card's downclock is less (300 300, iirc). I believe the standard single monitor downclock is 100/100 or 100/150 (I'm not in front of the PC with the 6850 at the moment).
Quality control sounds unlikely to me, more likely that SPCR got a special more silent version. Maybe there are some settings in the bios we do not see with RBE.
No multidisplay, multidisplay gives me 250 1000 (also a weird setting, which I cannot find in the BIOS, so must be in the driver I guess).
I tried the 10.10e hotfix drivers (from the SPCR article), these give me 100gpu 300mem (instead of 300 300 with catalyst 1.11a), no change in fan speed, still 22% lowest. Now back to back to catalyst 1.11a, which means back to 300 300 idle. This is definitely a driver issue.
The fan speed is still a mystery to me, something is stopping the changing of the PMW below 22%, or our versions have a different fan with different fan settings for the PWM percentages (but now I'm getting paranoid).
Quick follow-up to confirm that idle on the Sapphire model and the reference designs is 100/150 (core/mem). Given the experiences posted here, it sounds like Asus may have changed the minimum fan settings after sending out review samples (or, as you suggest, the review samples were not standard).Here
is a thread dedicated to the Asus DirectCU 6850. Perhaps other owners can confirm whether they are also seeing higher idle rates. There's also a link to a review
that indicates the fan will not run slower than 1500rpm (although obviously some here are experiencing higher lows than that). At bottom, the DirectCu can't be recommended for the silent aficionado given the other models available. The card also has higher native voltage despite a minimal factory oc (of 1%). See p.1, 9 of review here