I think that may be good advice in multi-family dwellings, or where houses are so close together, or where everyone's COVID-19 status is not known in a house.
For single-family dwellings distant from other houses or where everyone's COVID-19 status in a house is known, it would be okay to run AC.
Except you may not know if someone in the house has it or not until it’s too late.
Our house has always been open to the fresh breeze anytime it is between 40 and 90 in the daytime.