iOS "Done" Button Position

While browsing the App Store, I noticed something I find a little odd, and a little annoying.

If one browses the images (screenshots) of an App[lication], the “Done” button to close and return to the app[lication] info is at the top right of screen.

However, if one looks at the moving picture (video) which many have now, the “Done” button is at the top left of screen.

I can see no apparent reason for this difference (though that does not mean there is not one). Can anyone elaborate?

Maybe is it just an oversight on the part of the OS engineers.