Uh those are cases and they are third party.
My iPad case with kickstand capability is an Apple product, not third-party. Quality leather, bought with my iPad years ago.
So what? They were available for the iPad long before Microsoft incorporated those 3rd party case designs into the hardware of the Surface. . . It makes no difference. . . except to add unnecessary weight to the tablet portion of the Surface for when you just want to carry it. If you just want to carry the iPad, you don't have to carry the extraneous weight. You do with the Surface. All those extra grams of everything you include that are unnecessary for everyone total up to extra weight and add to the price.