It wouldn't have Diamond as it's the Pearl intro, and fake or not - it's going to be EXACTLY the same in the actual English versions of the game anyway as all they're doing is replacing the Japanese logo with the English logo.
Even if it isn't the genuine article, it may as well be.
Fun fact, I spent my first 10 minutes with my copy of Pearl just watching the intro over and over again. So, so, so winsome.
I then spent the next 6 or so hours playing it constantly and being sucked in so easily. I can't wait for the English version to actually have the dialogue aspect of it (and to make battling easier) to make it all that much better.