That has to be the most bizarre statement I've read in a while

It's a 360 demo, for the Japanese market, where the matter of sales and popularity is irrelevant for the console (for Capcom alone, comparing DMC4 figures doesn't favor the 360 there). Even if that were the case, it's a demo and not a full version.
Some people who on the fence about picking up a console for the game in Japan will likely go for a 360 to try out the game sooner than later. So if MS Japan arranged this, IT IS a smart move given the few surges in sales recently with a price drop and good software.
I reckon the PS3 demo will be out in late Dec or early Jan.