Sure, if you are transporting them via rail it would be the same.... but on belts, nothing stacks.
It's not so much about stack size as it is about how much you can fit / move on a conveyor belt. A lot of the setups I've used involve having a copper wire factory (or two) right next to the factory that uses them, no belts / buffers in between.
I thought the same thing, but I think copper plate stores 100 in a stack and copper wire stores 200 in a stack.
I don't know what that means for inserters. (like low density structures - can stackers move more of them, even though you can store less in one slot?)