Diamond and Peral was the Spring Release last year. Remember how Infernape dominated Spring Battle Roads in 2007. That is why Ambush was Created for Nationals.
DP was not a special case.
It was out in the US well before Worlds.
There was an issue with it being released later in Europe because of the delayed release of the D&P DS game there, so European invitees got a box of DP shipped to them.
But it was out well before Worlds. There is no comparison here.