This is the most pathetic "true test" I've heard of. Sorry. The game was already released on another system, no matter how well or poor it did there, so it'll never be much of a test of anything. Besides, it's not a very well-known game, either. I think if they sold more than 250k copies between both versions in Japan their heads would explode with happiness.
Reall, we already had a much better test recently with DMC4. It was a decently large game from an established franchise and while its legs haven't been holding up it did score the best (or at least close to it) debut on the PS3 so far while being multiplat day one. And it's doing pretty damn well compared to its predecessor for just the PS3 version.
DMC4 was a test. And the PS3 passed, if just barely.