It's not a fake. The model after the V5 has different names in different parts of the world. In USA it's the V5 Celebrity, and in Australia it's the V5.5.
This isn't the first time Bandai has used different names for the same model. The model after the V4 was called the V4plus in Europe, and the V4.5 in USA.
The main differences between the regular V5 and V5.5 (V5 Celebrity) are the types of characters you can raise, and the built-in games. They both use the same TamaTown (Tama & Earth Expo) web site. They can connect to each other, and can mate with each other.