If I remember correctly, even if the a/c is off, if the system detects condensation, it will turn it back on by itself...there's a lot of computing going on in the car...it's not like the 'old' days.
FWIW, BMW did some testing, and when it comes to a/c use and opening the windows with it turned off...above about 28mph, it's more efficient to use the a/c than to turn it off and run with the windows down due to the increased drag from having them opened. That threshold might vary on other cars, especially on an ICE.