No way am I buying that for my betta! To their statement that "they don't swim around a lot...our aquarium provides plenty of room for your betta to swim and play" I say, "pooey!" My boy is in a 5.5 gallon and he's swimming and exploring and even glass surfing! If I'm worried that my 5.5 isn't entertaining my boy enough, I definitely don't think that a half gallon will.
As others have said before me, bettas like their tanks wide, not tall. They want to swim without hitting something, not hovering up and down. Plus, pouring the water in to "clean" would probably stress the fish out waaay to much. It's like he's in a washing machine or something.