If you look at the last "Cold Storage" numbers you will see that the numbers for January were revised downward, and not just a little.
Furthermore, virtually all the "wrong" data came from the "Mountain" region. There are very, very few plants which would be part of the NASS survey. NASS likes to not let on but, I think there are only two.
So, how much were the numbers off? 172.5 truck loads! Some mistake!
USDA ERS tells me the "Commercial Disappearance" numbers will be revised.
You could make up a believable scenario that the numbers were a deliberate attempt to justify crashing farm milk price.
Additionally, many people rely on those numbers because they are supposed to be accurate. Besides, they are the only thing out there.