Though I love to pick the opposite side of an argument or issue most the time, I have to say it's blatantly clear to me that dungeoneering is more of a mini game than a skill. And with the way Jagex has been doing on content lately, it's no surprise they would try to sell dungeoneering as a skill rather than a mini game. Such a shame...

As for the generalizations, I add that just like a skill can be used outside an area or beyond its specific use, skills don't focus on a mini game or any small, limited area, at least for training purposes (construction might be the only small exception to that, though, since almost all building is focused around your house). Dungeoneering is just so limited in these regards that it's hard not to call it a mini game, one massive mini game.