No, it will come across as whining.
Yes, in the sense that they can write that the grading standards are very challenging (if that is in fact the case) or as @collegemom3717 says, that you are one of the best students they have ever taught. But they should not compare the grading to that of other schools.
You should assume that the AO’s are quite familiar with grading standards in your country, if not at your particular school. Really, don’t worry about it, because there is absolutely nothing you can do about it.