Somebody is obviously trying to cover all the bases. That’s just good thinking. If ghost are real, they get zapped. If they aren’t real, they get to chase a group of adolescents all over the place for about 20 minutes before said adolescents figure out it’s not a ghost for the umpteenth time.
Then fred takes the mask of the ecto 1 and says it was old man cribbins the whole time. And the ghosts were just sheets on strings. And the gatekeeper was just elitist goth musicians.