Not being a doctor, does this mean "Be careful if converting statistics to real numbers. A false-positive percentage relates to the number of tests, not to the size of the population"? So you can't estimate the number of cases in the general population based on the results of a tested sample, the reason being that there are too many other factors to consider.
It means that WHO now agree that PCR tests are being cranked through an excessive number of cycles so that "weak" positives are for example being generated by people whose immune system has killed off the virus and all that is left are viral fragments which are non viable.
These people are not unwell. They can transmit nothing, but none the less are labelled as "cases" which is dangerous nonsense but provides scary numbers which suits the purposes of the lockdown fanatics.
This is what the likes of Dr Mike Yeadon and others have been saying since March 2020. And been branded as dangerous Covid deniers for their trouble.
Countries which follow this updated WHO guidance will almost certainly start reporting significant reductions in Covid cases.