When a runway is not in use but is published in AIP as a useable runway then it makes sense to refer to it at all times as if it an active runway. This way there is no confusion and it ensures there is no risk of an incursion. Good example of this is Gatwick where the standy runway is used as a taxiway when the main runway is not available, but it is always referred to as 08L/26R and I believe vehicle drivers must request ATC clearance to enter even when it's used as a taxiway. So it does happen at other airports.
It's ATC's way of making sure they and you do not enter or infringe a runway without clearance.
The take-off/landing clearances take into account other conflicting runways are clear of traffic.