This suggests to me that the noise figures may have come from semiconductor datasheets, not measurement of actual preamps.
Could be, like noted before, the soldering on it looks handmade. Maybe they have limited test equipment ? The datasheet also shows how much the gain is affected by input voltage. From what Ive read from other users of the CM0264 and its cousins, the power supply voltage varies from individual unit to unit. I have 18 vdc on mine, some have reported 22 vdc and one reported 12 vdc, heh.
Im not ragging on the unit, it works very very well. Compared to my old Radio Shack preamp its like night and day. I do have pictures of the RS cut apart, posted in the preamp thread, if you want to get a good laugh.