Thickness, not hardness, is the factor that determines flexibility. I owned a Konosuke petty that had some flex, and I would expect that the Ginga is no different. If you want stiff, get a Hiromoto Gingami 210 suji.
I have one, its not a stiff knife, but its not too flexy either. I don't use it for anything heavy duty, so I don't mind the small amount of flex. It's a very light knife.
I have the white #2 version. I agree with Dusty...some flex but not much. I get approx 3/4" of flex without worry. Feels like a small, thin suji to me. Real nimble knife.
i like it a lot.