A national culture’s product philosophy is what it defines as a good product. The characteristics of a good product. Its character. Because there are differences between national cultures, there are differences between product philosophies.
If the American and the German product philosophies were the same, or similar, their products would look the same, or similar. They would have similar characteristics.
But often they are not the same, not even similar. When the two cultures collaborate they do so in order to produce a result, a product, a service.
The better they understand the differences between their respective product philosophies, the better they can produce great results.