That's definitely not from either the Disneyland's Submarine Voyage nor from Magic Kingdom's 20,000 Leagues Under the Sea. It also isn't from the 20k exhibit they had early on at Disneyland. I don't see how this would fit in pretty much anywhere else. And while very cool, it looks very subpar...
It was always intended as a tie-in to the movie. They just changed the name and a few things to help reinforce that idea. The movie had been shelved for years and the ride being developed helped push the film into production.
As big as a Haunted Mansion fan that I am, I would skip the stretching room if it meant I didn't have to wait in a 4 hour line due to the elevator capacity. Plus you get to see a rarely seen corridor even if it is not the best themed area.
For those that don't know, it's a reference to this concept art by X Atencio.
In one of the early drafts of the story done by Atencio, the black cat played a role that would be evolved into what the raven/ghost host character does in the ride and earlier drafts.