Most designs of wbc have ready access to the space between the lifts and the inner boxes already.
Some Eastern double walled hives have a bridge/tunnel from entrance to brood chamber, but I haven't seen such things on a wbc !
As Victor states,there is allready access between box's and lifts,plus wbc normally have cone escapes for bee's to get out. Have seen some adaptations to lifts for doing A/S, like a round hole and tube,or cut out hatch in lift for bee access. But can only take a guess that this entrance in the porch lift has been made to allow rear access for a varroa insert test tray,home made modification.