Compared to what, a rhinovirus?

> you're positing a very large undetected outbreak of an itself-undetected variant strain of COVID-19

From the linked study, it appears that at least one variant has been detected:

"Population genetic analyses of 103 SARS-CoV-2 genomes indicated that these viruses evolved into two major types (designated L and S), that are well defined by two different SNPs that show nearly complete linkage across the viral strains sequenced to date."

How would PCR test results give us any sense of the relative spread of these two strains (or indeed others)? Is it possible that you're motivated to dismiss ideas that challenge your understanding? I'm not convinced that it's the correct explanation for these observations, but the argument that it's impossible seems pretty weak.