Dude, I normally bristle at the way Penello gets kicked around here, but that answer is laughable.
If the answer is "this was the real UI, we just trimmed out the parts that show the bits still under construction," say that.
If the answer is "there are the sort of small, annoying bugs visible in the current build that are on schedule to be addressed leading up to the launch," say that.
If the answer is "press release materials are further from the actual development environment than you assume, so there's a big delay from what we're working with now," say that.
If the answer is "We've got some newly introduced issues with the way the different elements interact in our test environment," just say nothing and don't bullshit us.