Not necessarily. The prof could choose to make grades relative by subtracting rather than dividing.
If that was the policy, then someone could've boycotted the boycott by going in and trying to score exactly one point on the exam, possibly after everyone else left. Then everyone else would score a 99.
It would have at least given everyone something to think about afterwards.
The reason this situation seems unusual: The prof's grading system has a division by zero bug.