One thing earlier testing would have done is driven down the death rate (the %).
Remember how the 3 to 4% got used as predictions of how tens of thousands would already be dead by the FR resident experts on pandemics?
97-99% of the testing being done is negative. It would take 10’s of millions of tests to effect the calculation of the death rate.
According to the experts death rate is only an estimate at the best. There was a theory that there was a pool of infected mildly sick but the testing here & in other countries is not bearing that out.