Your analysis is correct which is why lots of people install bars/cages around window AC units.

Note that portables with one hose are a very poor investment. They are very inefficient compared to two-hose models.

On the window A/Cs that I have owned, the window was "locked" in position so that it could not be raised (allowing the unit to fall out) without unscrewing a clip.

A burglar that slashes the "curtain thing" would have to lift the unit out of the raised window to gain access.

With no window, the burglar can throw a few pieces of duct tape across the glass pane and smash the window.

Just some thoughts.

By screwing the upper sash to the lower and making sure the screws holding the AC unit are more than 3/4 inch long.

Put unit on 2nd floor window and hope burglar does not have ladder.

Not something I ever thought about. I guess I live in a very safe place (says everyone). I've never seen any house with cages around their A/C unit. All of our window units are on the 2nd floor.