Nice numbers.
Japanese car makers use to do this a lot in the mid to late 90's. There was a unwritten agreement between all the Japanese manufacturers to state their HP numbers at a maximum of 280HP. It had to do with higher insurance rates in Japan. But that was stopped a few years ago.
That's why all the Japanese sports cars of that era and the same HP quoted (3000GT, Supra, 300ZX, Skyline, etc...). It's only in NA that the really numbers where stated.
What I don't get is, if you're buying a 627HP Vette or a $90,000 GT-R do you really care about the higher Insurance rates? Or is there a huge premium increase if you break that 500HP mark?