I just don't see what will hold the doors flat against the frame
This will be done with the flush bolts that are fitted top and bottom to leaves 2 + 3. The multilock is mainly for door 1 with the added security that if one day i did forget to lock the flush bolts (doors 2+3) it wouldn't be a case of simply pulling away from the frame as you state.
Not sure if that makes sence :?: