I think that's basically saying a "dungeon crawler" must be RPG-ish - excluding games that are just finding your way through a 3D maze. Honestly I think that's pretty well already covered by the rules above and below it though.
Should say though, that the depth of RPG actually required here is very low, so there’s no need to do skills, inventories and the like unless you want to. But there need to be some sort of stat such as e.g. health and a self or a group of protagonists.
