In central air conditioning, unless you have an outside air mixing intake, there is no reason to turn off the A/C since you are just recirculating house air.

The main concern is for window units that have a setting for taking in outside air or if you live in a very currently built home with provisions for outside air exchange.

Another warning that should have been issued is to not use any exhaust fans in the living area. Mother nature abhors a vacumn and air being exhausted will be made up with outside air coming in through any unsealed area from the outside.

Few of the YA-HOO'S that issue these kinds of warnings are sufficiently schooled in HVAC-R.

Bountyhunter