The first assertion is wrong.
If we rest 1 million extra cases, and they all come out negative (”really negative”, based on a working test), we know it hasn’t spread.
But if 900,000 of them come back positive, then those sure as heck ARE new cases, because they’re really infected.
If you mean, those 900,000 were there anyway...they were, but they were assumed negative until the test.
I’m disputing using the rate the cases are discovered- which is what “confirmed cases” tell us- for the rate of spread.
And that’s it.
Yes, I think the point is obvious so maybe I’m not explaining it well.