They could vary the cycle threshold for any reason altho i have never been asked whether i was vaccinated when tested and then operated on. But i think whoever is administering the test or performing the test can vary the threshold cycle to increase or decrease the case counts. You will never see the cycle threshold along side the case count. Some where in this mess someone I think in florida was requiring the cycle threshold number as part of the test result but i’m sure that was just ignored.
It’s certainly out of my realm of expertise, and I suppose there may be some scientific rationale to vary the cycles. But if so, it should be random and for a specific scientific purpose - not segregated by type. I have heard, but do not know, that these types of tests were not originally designed for this purpose and that running high cycles will create lots of false positives. Sort of like “fake it until you make it”.
On the flip side, the official case count in the USA is about 10% of the population. But the Red Cross in March 2021 tested all the donated blood for antibodies and reported that 20% of donated blood from unvaccinated people showed antibodies. Now that may not be a perfect representative sample since perhaps a disproportionate number of blood donors are hospital workers, firemen and police etc who are front line and more likely to have been infected. But it does make me wonder what the real number is - how many Americans were infected and never even knew it because they had either zero or extremely mild symptoms so they never bothered to get tested? Or, they got it before we had the tests?