Y'know it's amazing I've both never thought of this before and also never seen another Manga that has thought of it, but as someone who generally hates the Arbitrary "Ranking" that happens to Magic in Manga like this, it becomes infinitely more tolerable and acceptable when the Author actually goes the extra mile and puts a Name to their silly scale. "Flandol Hand-to-Hand Combat Scale" immediately elevates the idea to something that's more real, simply by adding the name of the guy who presumably codified it.
Same reason why any Story that refers to towns by what type of town they are, or just says "Kingdom A" is one I immediately lose any interest in.
See the problem with the arbitrary scales is that they are used by Lazy Writers to avoid having to do World Building, and to avoid having to figure out the relative Power Levels that their abilities have and see how they would be considered. You don't need to think about how other people would react to a certain ability, you just say its an "A" Class Ability and then how impressed people are derives from that. You don't need to think about how the country works because you just say "Harbor City" and don't even bother to think of a name because there's only ever going to be one Harbor City.
And if you the Writer weren't interested enough in your world to flesh out these details, why should I the Reader be interested enough in your world to actually read about it?