[native_samples]

It's not clear they're actually more infectious. Claims that they are come from invalid methodologies like comparing the growth rate of one variant when it's new against the decline rate of another when it's old, or making assumptions like the one you just made above. Generally, it's good to treat any claim made by the field of epidemiology as suspect. They aren't incentivised to use statistics correctly.

Re: PCR:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8166461/

In light of our findings that more than half of individuals with positive PCR test results are unlikely to have been infectious, RT-PCR test positivity should not be taken as an accurate measure of infectious SARS-CoV-2 incidence. Our results confirm the findings of others that the routine use of “positive” RT-PCR test results as the gold standard for assessing and controlling infectiousness fails to reflect the fact “that 50-75% of the time an individual is PCR positive, they are likely to be post-infectious”