comment: >
  
  Sure, there may be some mitigation but I don't see how this makes the conversion of in-class percentage to 4.0 any better.  To receive a 3.5, one must have an equal amount of A- and B+ (of the same credit value). Meaning that a typical 0.5% of in-class, in all of one's classes, has the weight of 0.2 on the 4.0 scale. Thats a massive step for what could simply be a student getting a single question wrong in every class.
context: I would argue that a mitigating factor is that GPA isn't really used for individual classes, but over the whole education. In that time frame, we might assume that a student's course grades will be randomly distributed about their "true competence" in that class, so in fact an 89% student is only slightly less likely to get an A- than a 90% student. Thus, their average grade should tend to reflect that, where they'll both be hanging out around a 3.5 over the forty or so courses that constitute a degree.