It's important to include the word "reported", and I prefer "reported positives."
It makes explicit that they're not cases. Some are symptomless, many never go to the hospital.
It makes explicit that they're just the tests that come back positive. That's clearly less than the number of people infected.
It makes explicit that the tests aren't people. Some people have more than one test done over the course of a week or two, and if both come back positive they're not "two cases."
You can tell that to some people day in and day out, and it's like telling a prospector that iron pyrite is fool's gold, demonstrate how to tell the difference, and have him nod. But then the next lump of pyrite he says, he shouts, "Gold!" because it's golden and glittery and he's hankering for a bit of the real stuff.
If we test a lot we get a lot of "cases"--reported positives--and if we test little we get few. The people that think more testing means more people are infected are on the same level of comprehension as those who think there'd be less if we tested less.