I suspect that in most cases(and I would feel the same way) it's not the fear of testing positive. As you say, if it happens than so be it, you do the right thing.
The issue is more about if a colleague tests positive... What happens to the rest of the staff? How do you classify as a close contact? If I happen to go to the same washroom, do I get sent to quarantine for two weeks? Again, this would seem paranoid if it were not for the whole exam hall that was sent to quarantine in one swoop earlier.
If they set and state strict conditions to be considered a close contact then it allows people to better protect themselves against an arbitrary order to be sent to quarantine.