Although you are correct in that the door hinges upwards, only the top and outer portions do so. The slide back is left in the door way, blocking half the exit. This unit hinges at the bottom, the idea being that when the door is opened, the slide pack falls over the side of the fuselage, locks on a pin and deploys automaticaly.

Unless the slide pack is removed completely, or has been deployed in an emergency, it is impossible to walk through the upper door.

Hope this helps

FB