Rossman's are flush on one side.
I do believe, and someone will surely correct me if I'm mistaken, that the inner covers with a shallow recess on one side and a slightly deeper recess on the other are actually the 'proper' design. They allow appropriate 'bee space' on both the top and bottom when properly installed. The ones that are flush on one side, I think, are done so only because it is simpler to make that way.
Let me never fall into the vulgar mistake of dreaming that I am persecuted whenever I am contradicted. - Emerson