You are technically correct about the BAC, but they definitely cannot have one while "on duty", there's an 8 hour limit between your last drink and flying and some airlines have longer time windows by policy

https://www.law.cornell.edu/cfr/text/14/91.17

Not quite, there's also a rule that you can't operate an aircraft within 8 hours of consuming alcohol, aka. "8 hours bottle to throttle".