I do not know the answer to this. I assume there is less hard data to work with when trying to claim a statistical certainty on a certain type of generally clean produce which can be affected by numerous factors. Anyways, perhaps the osrim would in fact say it’s problematic in certain cases. Thankfully it’s permitted for the consumer regardless.
Either way, an explanation is still necessary why Halacha should ignore hard reality.
This analysis doesn't really account for a couple of potential statistical issues:
1. The analysis assumes that the 1000 cows being milked are a representative sample. Even if there are 10% of treifos across the whole population, that doesn't necessarily mean that a given non-representative sample has the same characteristics. To use an example from further up the thread, let's say a farm has a cow population much younger than average (and younger cows have a lower treifa rate). That changes the calculation significatnly.
2. The analysis assumes that the occurrence of a treifa in each individual cow is an independent event of the same probability under all conditions. That seems to overlook that conditions at a given farm or dairy facility might lead to fewer treifos because the cows are healthier than average.
3. Even if the average incidence of treifos across all cows is 10%, the analysis doesn't consider whether there is a difference in milk production between a treifa and a non-treifa. If a treifa were to produce less milk (I assume hashgachos may have done such an assessment), that changes the bitul b'shishim analysis even if 10% of the cows producing the milk were treifos because the total milk produced by the treifos is not necessarily proportionate to their total number.