Seems a bit harsh - If I've spent the XP to be able to call '10', but am only calling '5' for about half the blows I'm landing, doesn't that mean I've wasted a lot of my XP on something I'm not using? It's a bit different with abilities that cost Essence to use, they are clearly something that's big and special and unusual. But my grades of Strength or my Weapon Masteries are always "on".
not a rule but a piece of guidance
You are always strong, always skillful but you don't land a perfect blow every time.