My understanding is that the comments weren’t about any exams. The comments seemed to be about the evaluations that the professors were conducting at the time.
So am I correct that you find it more plausible that Black students had the lowest grades every year than that the professors were biased in their grading?
Now we're getting to the truly interesting part of the discussion. Why did the professors notice what they noticed? Logically, I think there are two possibilities. First, the professors were wrong and the trend does not exist. I would be inclined to find bias of a different nature if that were the case, but it ends this discussion since it would establish that the phenomena does not exist. I would suggest proceeding under the assumption that the trend exists at Georgetown.
I read as much as I could find on this particular case before drawing my conclusions. I have not studied this topic in detail, so I have relied upon a variety of articles with differing perspectives, as well as my own view of the video several times and the transcript of what was actually said. This article provides several explanations:
https://reason.com/volokh/2021/03/11/adjunct-law-professor-fired-for-saying-to-colleague-a-lot-of-my-lower-graded-students-are-blacks/
Affirmative action is one explanation mentioned in that article. It makes sense. If GPA and the LSAT are indicators of law school success, than those with lower scores compared to their peers will, broadly speaking, perform at a lower level. The article affirms that this has nothing to do with race: "virtually all of the black-white grade gap disappeared when one controlled for LSAT scores and undergraduate grades." Meaning, if the black students who received acceptance to Georgetown went to schools where their GPA and LSAT aligned more closely to the median, perhaps schools like Wake and UNC, you would expect this trend to disappear.
Stereotype threat is also mentioned as a possible explanation. I think that is also reasonable. In law school, especially the first year, professors make frequent use of the Socratic method. I'm sure that I asked some dumb questions and made some dumb answers. However, I never once worried that people would hear my dumb question/answer and think "he's here because of affirmative action." This concept could actually help explain why black students' grades were lower in a class where participation is accounted for (which was not an uncommon grading practice in my experience).
I tend not to share much about my personal life, but my wife was a minority law student for about half of our marriage so far. I know a little bit about how law school works, and I've had the chance to see some things differently through her perspective. I do not think for a second that a single grade she ever received was altered in any way by her race, positively or negatively. However, I would understand if she experienced hesitation before speaking up in class in a way that I never did.