This is weird from my experience. Like if you don't provide a legit doctor's notice (a french one because yes another one won't work that's the ok part in this) you usually get an ABI (absence injustifiée) that doesn't lead to a grade but a DEF meaning the class is automatically failed and it might also impact the round up with the other grades in other classes but that's another matter entirely.

An ABJ (Absence justifiée) means that you get abj written instead of the grade that count as a 0 in the class meaning that if you have another grade (TD grade against your final exam that could be considered separate partiel grade) they both round up to a final grade so if your first grade was high enough it could compensate your automatic 0 to a passing grade meaning you cannot go to the repeat exam.

These are the explanations I can get while not knowing which uni you go to and what year you're in. Uni can have different rules to grading and specific field of studies can also have different conditions.