I think you hit it spot on. Sure it isn't canon DND....but I didn't want that anyway tbh. Developers have their own ideas of how to implement things and that's fine - so long as they do it will. And I believe that obsidian did a fantastic job with implementing their system. I can finally have the wizard that wields a sword instead of a damn staff (as in every other rpg). I LOVE THAT! I can't tell you how long I've wanted a wizard to be able to wield a sword rather than a wand or staff. It's a relief and thank you Obsidian.
Now don't get me wrong, I'm still learning the differences between crush/pierce etc....but hey. I love this game.