my bad I will explain it with more examples. usually if you want to bake normal map for mirror object you take the half uv and send it to other side and bake it right. for this example, it's not mirror object so doing this will be fine for baking ? as you can see I share uv island for the top and bottom so is this process…
Are you asking if you can have two UV's in the same position in your UV space? If so yes, but both will end up exactly the same and if you for example paint on one side you will also paint on the other side automatically.