Just to say (not taking any credit for the research, info from SciresM):
The Diancies which lack the 3 IVs at 31 are a completely different wondercard, and (most likely) aren't fixed by the update (sorry to those affected).
Also a way to skip the cutscene if you haven't received the wondercard yet (and don't have any other wondercards uncollected on your save):
• Save where the lady who gives you the Pokémon would stand.
• Receive wondercard.
• When you continue the game, she will be one step out of place; receive the Diancie and the cutscene will not play.