A multinational like Amazon has to balance what works best in a particular market with retaining a consistent identity across markets and having shared functionality between different locations.

Why would this be the case? If they want to maximize sales in Japan they’d surely provide the best format for the Japanese market, as any views from other countries would be minimal. Maybe if it were in Europe or another site that serves markets that are in close proximity to other ones, but no one’s ordering things from an isolated island with a high population if other options are available. And even with varying options the format doesn’t need to change.

I remember awhile back looking for hot sauce (as in something that’s actually spicy instead of like tabasco bullshit, which is (or was at the time) uncommon in Japan), and the amazon options just listed sellers from the US with high shipping costs. So when Japanese people want foreign goods, why wouldn’t amazon provide a format that “people want”, while still pulling from other markets?

The fact that they don’t do this leads me to believe that the rakuten layout isn’t the only way to profit in Japan, and in fact might not even be the layout that most Japanese people prefer.