The S is misleading. It's less about simulating, and more about exploring to understand. Immersion, abetted by, but not necessitating, any mechanical simulation. In particular, in my view there is no need to be simulating some genre. That's a red herring.The 'S' in GNS refers to simulating SOME GENRE (or maybe more specific material, I mean you can go as specific as you want there). I think you could make a case that DW has an agenda to simulate classic dungeon crawl narratives. I really am not knowledgeable enough about it to make any statement as to whether or not that qualifies in 'GNS Theory'.
EDIT But you can use DW to serve any agenda, and it some concepts in DW are very suitable for a sim agenda IMO.