Yes, indeed it does seem a little odd. I wanted it that way. Leaving aside my metagame motives for putting it there, it reflects demon psychology. Every demon above the lowest ranks has teleport without error, once every 6 seconds, for all of eternity. The only thing demons need doors for is maybe getting an initial look at a teleport destination (demons of the better sort usually scry) and shlepping around furniture. Which demons need doors then? Demons that shlep furniture around. And mortal servants need them. To a demon, every entrance is a service entrance, and using a door is like stamping "menial servant" on your forehead. Nobody important walks to room 29.
About the doors - yes, they open with the same way from either side. I figured the corridor was part of 29. And, so as not to disturb anyone unduly, I will amend the name of the sport to "q'tcherbi'jin," and hopefully that will fool JK Rowling's lawyers.