We had a ginger tom cat a good few years ago. We had a cat flap not unlike this one, but it was pre tog so it was activated by a little magnet on his collar.

We could set it so he go out, but not back in. It didn't take him long to figure out the door only opened outwards, and when outside he could hook a claw on the lip, pull the door out, get is head under and back in the house!

It was pretty impressive the first time I caught him doing it.

So all cats out, could also meant all smart cats in

Cheers

Cris