We used Mohs' scale in Earth Science class to measure the hardness of rocks. If we could scratch it with our finger nail it meant the rock had a hardness of 2 or less. If not it had a hardness of 3 or more. Then if that rock could be scratched by another rock we would assign something greater and if it could scratch softer rocks we'd give it something less. Eventually we were able to come up with a self-consistent order of hardness for all rocks in the data set.
I do not see why you are comparing this to quantum computers.
Why Mohs' scale and not the Richter scale or the Kinsey scale or the pH scale?
To answer your question: There is no such scale I know of for quantum, classical, hybrid computers. The reason why is probably the fact that those three (quantum, classical, hybrid) are the only things on the scale worth mentioning, so it is a ternary scale (1,2, or 3) not something more sophisticated like a 1-10. We therefore don't have to use numbers and can just use the names, which are more descriptive, self-explanatory, and therefore clear.