If it's real, it's definitively an anti piracy measure.
Yeah, it definitely couldn't be a prank from a ROM hacker that got spread... oh wait.
First, note how Bulbapedia doesn't make reference to it (or any other important site at all)
Second, think about it: it seems kinda unprofessional for Game Freak to put such a relatively strong hidden message when they were so busy turning all the gamblers into gamers and useless **** like that.
I'd like so see a pic, just for ****s and giggles of course.