Lassik, if he meant "that drawing isn't an official Rubik's brand cube," then why wouldn't he just say that?
You're right, though... we're just going to have to disagree on this. My interpretation of his comment was based on my own reaction upon seeing the T-shirt design, and it had nothing to do with whether it was an official Rubik's cube or not.
At first glance, for somebody who has solved the cube thousands of times, it just looks wrong. Normally you don't see a cubelet with white and yellow adjacent, and this drawing has two of them (an edge and a corner). It also has a red/blue/green corner, which is impossible with the normal color scheme.
So I thought, okay, maybe that's a Japanese color scheme. But it can't be the Japanese color scheme either, because the white center isn't opposite the blue center, and the red/blue/green corner is counterclockwise when it should be clockwise. So it looks bogus, even though it isn't.