To my way of thinking, and their research into the literature I think supports this, a large number of high grades for a given course section should indicate that learning was successful - the instructor should be lauded for being a great teacher! However, they are not so naive to assume that all grading practices are similar nor that all teachers have the same criteria for grading. And thus raises their point that comparing grades between teachers, courses, programs, institutions is a messy, unreliable process.
So what is to be done? They suggest keeping a critical perspective on what grades mean and to consider changing our grading practices so that we are not discouraged from the potential increase in marking that sometimes accompanies active learning strategies.
Indeed, I suspect this is Tanner's reason for publishing this paper. Her body of work supports a change in how we teach from one that is instructor-centric to one that is learner-centric. This paper, I think, is an attempt to provide instructors with an approach to grading that will free them up to consider using more active-learning strategies in their classroom. Active-learning teaching strategies do not necessarily mean an increase in marking load - if we re-consider how and what we grade.
Schinske, J., & Tanner, K. (2014). Teaching More by Grading Less (or Differently). CBE-Life Sciences Education, 13(2), 159–166. doi:10.1187/cbe.CBE-14-03-0054