The German article states that this page was up for a "brief moment", which essentially means there's no way to verify whether it's true or not. I highly doubt the game's already been PEGI rated since that normally doesn't happen until very close to release (there's no point in rating an unfinished product) and I think the previous Diablo games have been released in late June, hence the release date you see there.
German game rating may be different... It differs per country.
I think it's fake because if Bllizzard will give out a pre-order release date they'll for sure would start at their main site, not the german version.