It wasn’t the scare, it was the use of the scare in such a way as to cause an injury that occurred outside the premises, that was being brought up in the court.
This could well be the court’s way of saying fie on all the foolishness, meaning the haunted house and its patrons, and taking this legal dodge, throwing the issue literally to hell. Legal can have nothing to do with righteousness, but then neither does this ginned up scaring.
It wasn’t outside the premises, even though he thought it was, because he went through a fake exit.
Oddly enough, real and fake exits have long been a mainstay of sideshows. A no lesser light than P.T. Barnum used such a gimmick, signs that encouraged the people inside, “This way to the Egress!”, touting “the egress” as a big attraction, when in fact it was just a synonym for Exit. People would be outside on the street before realizing they had been skunked. And no readmission without paying again.
The bottom line is that the court was right.