Sorry, what I wanted to say is that adding it might create a problem for routing.  Since it is a straight line, routers will always take it as a shortcut.  Remember the problems we had when people complained that OSM encourage hikers to use private paths.  Stairs and gates are a penalty for some routers but not all, so most routers will advice people to walk across the building.  (Of course, this is legal, so we can say we don’t care and add it nevertheless.)