Overseas scalping is also the reason why hardware sales are as high as they are. PS5 was never going to be as popular as PS4 in Japan. But the scalping has made hardware sales higher than they should be and software sales lower than they should be.
I wouldn't say thats a given, because even with less overall demand, the PS5 could be more front loaded than the PS4. Meaning it sells less than 9m, but sells to smaller userbase a lot quicker, having it track equal to PS4 for its earlier years and then drop off later. Either way 2023 is going to a very interesting year to watch its Japanese sales