At least you can give this cat owner credit for being kind enough to provide their cat with a play area. I used to have a six foot play area for my cats, but eventually it had to go to make room for things that I enjoy. Plus one of my cats is too fat to have climbed it. She could only enjoy the first platform. I didn't want her to form an inferiority complex from my other cat always being higher than her.
It may seem like this is torture to the cat, but think of how cozy that cat is. It's like being back in the womb, if you shared the womb with a fish. I don't want to see what kind of familial situation would have to occur for there to be a cat and a fish in the womb at the same time, but in theory it's a sweet thought.