I'm sorry, but that article is incredibly poorly written. It focuses more on Claude and Marc, with a brief paragraph at the end saying that it got plugged back in revealing the lost laugh. He even states that he doesn't even know if Marc or Davis was even responsible for this "lost effect".
It doesn't mention at all when the laugh was disconnected, how it was missed by maintenance, employees, and fans who were familiar with the ride and who's jobs were to make sure the sound for the attraction works. It doesn't talk about why the laugh is or isn't at other mansions.
If that's the best article on this effect, I'm gonna need more since far worse fallacies have been perpetuated by far more reliable sources. The Haunted Mansion is a cesspool of myths, legends, and artificial trivia that plagues the fan communities. So much misinformation has been perpetuated for decades that I'm incredibly skeptical of stuff like this and its history.