I can think of several reasons why women might be drawn to it. One is that you aren't cast into a male or female role; "you" are the avatar. That might explain some of the appeal. Two, there's no violence or killing. Three, the game revolves around the family (albeit a demented one). I think all those things make a difference.

Also, it's the puzzles that are difficult and complex, not the interface. I think not only appeals to many women but many people who don't play games. They might be put off by something with too many buttons.

Maybe "Zen rock garden" is going too far. The world is actually more like a...modern art museum? Or perhaps some type of modern art sculpture garden? Hard to explain, but it's definitely more "artsy" than most games of this type. Just look at the style of that rocket ship, for instance.