As with p values, having a bright-line threshold, causes curious behavior. In this case, scoring below 30 on any subject (a 30 or above is required in every subject) and failing the exam has arbitrary negative effects for people, so teachers usually try to prevent people from failing if there’s an easy way to do it, but a deeper root of the problem is the idea that it’s necessary to produce a certification that’s the discretization of a continuous score.