Why COVID-19 Testing Positivity rate matters (my humbly offered opinion)

It's not the primarily the reason we might think--namely, that it indicates a high proportion of the population is infected (although it may well indicate that).

A high positivity rate indicates INSUFFICIENT TESTING in the population at large. We can more or less assume that large-scale groups of patients who present themselves to a hospital or clinic for testing will have more or less similar positivity rates. When a state or municipality reports a high positivity rate, this indicates that they are not actively engaged in testing the population at large (surveillance testing)--large groups who would show a low positivity rate. Hence they will not be able to locate hotspots or do contact tracing to contain the spread. (Remember contact tracing, that quaint old-fashioned idea?)

I gleaned this from looking at this site, where high "positive test rate indicates insufficient testing." But I have not heard this explained by any of the experts, anchors, or reporters on CNN or MSNBC.

https://covidactnow.org/us/fl?s=716119

Anyone here with knowledge who wants to weigh in?