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.