I've always been under the impression that anything designated with letter grades actually represents a number for effective purposes. So, for example, A+ might mean anywhere from 95 to 100 on a scale where 100 is best.
In fact, I think WIS should remove the letter grades and show us the actual numbers. Remove the ambiguity and replace it with more knowledge of what is really going on.
I also think WIS should show us full player ratings rather than just integer values. If they improve in fractions, show us the fractions. I know it creates a lot of decimal points and more work, but show us what's going on.
Sorry, sidetrack. Anyway I think the values can be different when the letter shows as the same because I think the letter represents a number value.