Ric, let me first say that I can absolutely see that it needs attitude locking for multirotor Acro, so no disagreement there
But I don't think you're comparison with the static margin and dihedral effects from a fixed-wing makes sense. As long as you have a well balanced multirotor without anything dangling from it it shouldn't produce much unwanted moments during flight and maneuvers on it's own. When you do a 4/4 roll in Acro with a properly tuned quad it will stop the roll motion when you put your roll stick back to center and since you cannot leave it on it's side or inverted very long anyway it will look almost as good as with attitude locking. Of course it will drift with time.
For fixed-wing, I personally would actually benefit from attitude locking because I'm a bad pilot . Because with locking when doing a barrel roll with a large dihedral angle I wouldn't have to care about yaw and pitch control myself. But a good pilot will know the properties of his plane an naturally counteract it while flying so he doesn't need attitude locking.
My primary argument for/against attitude locking is related to the natural behaviour of the vehicle you fly. A multirotor has no natural behaviour except falling to the ground, it's a flying brick , so give it attitude locking and it flies like the perfect brick. From a fixed-wing on the other hand the pilot expects a natural behaviour so it doesn't necessarily need attitude locking but some still might want it.