KnC is skipping a testing methodology used by the vast majority of the ASIC industry: chip level testing to make sure they detect faults at the chip tester and not in the assembled product, where they might not even know if the cause is a defective ASIC. Rather than stopping or sorting the bad chips at the fab, they pass them on to their customers. Again, which hopefully will receive miners above the later announced rate.
Once they receive the completed machines they'll go a burn-in and anything not within specs will simply be set aside and they'll move to the next device and send you that one. It's not a big deal yo.
Then throwing away a full PCB containing working chips or go through the process of re-balling, re-flowing the BGA's? That's expensive, especially if the ASIC yield is low. I can't see why they are skipping this common simple test methodology for the price of possibly throwing away almost complete miners. But what do I know, perhaps is related to some requirement or incomplete procedure given by the undisclosed mysterious ASIC vendor.