Coupla things going on here. First, scientific understanding evolves. “BUT IN APRIL THEY SAID” yeah, that was then, this is now new information is synthesized and applied.
But also, the CDC has been compromised and should be regarded with extreme caution. Or at least a Nobel laureate, former director of the NIH and former director of the NCI thinks so. https://www.google.com/amp/s/arstechnica.com/science/2020/09/ignore-the-cdc-former-top-health-experts-say-some-states-already-have/%3famp=1