If you look at Mathijs’ various statements, it was designed for and around Xbox. Memory limitations with regards to animations, using stock everything where possible to ensure compatibility, the list goes on.
I’m not sure why it ISN’T available for Xbox; it was submitted to MS already. He said their first priority is to get it onto the Xbox, which to me implies that something is wrong. They gave them priority through the Marketplace for launch and the update, I’m not sure why the Xbox release wouldn’t have had the same.