that's a rule and it's around now for 2 years...
It's for making tabletennis more "fun" and more understandable for others so the tv-channels would pay a lot for it...
(even the size of the balls changed: 40mm and not 38 mm)
check this site out: http://users.pandora.be/luc.calluy1/meerdaal.htm
I'm still with VMS D (3the now)