Maybe, but in this specific story, the claim is that a teacher first says it's OK, that the student followed the marking criteria he was given, that the teacher

Maybe, but in this specific story, the claim is that a teacher first says it's OK, that the student followed the marking criteria he was given, that the teacher during the course of the project still said it was OK and that then, at grading time, the teacher turned around completely and all of a sudden said that he didn't understand anything about it, and therefore had to fail the student. Many dysfunctional examples from systems across the world notwithstanding, this particular one doesn't pass the sniff test.