Don't get me wrong, I'm not saying the X0 project is a hoax, but I could do those screenshots in Photoshop, and it wouldn't require donations or years of work.

It's not really proof of anything, that's why people are asking for something more.

Heck even people that do game modifications usually have progress bars like:
Coding: 5%
Modeling: 25%
Skinning: 20%
etc.

It just gives an idea of what's being done and in what time frame.

Wow, that sounded much nastier than I meant it too.
But really guys, why the mystery?