Interesting.
I think it makes sense. Namco expected people to store them stacked vertically, with the front label facing up, and the top label would be oriented correctly and you can see what game it is in a stack.
But I think a lot of people thought it should go the other way. Whether they were looking at how it looks inserted in a Famicom or they were wanting it to match how Konami carts were, most ended up upside down.
I have two Namco carts with top labels. Both are upside down.
