I don't see it as "really news," but it is a confirmation that Middleton - not Montgomery - officially speaks for the organization, to other owners; e.g., at owners' meetings. When ownership meets to vote on things (think ratifying the new CBA when it's finalized), Middleton is in that role - not Montgomery.
It's another formal step taken by the organization, and approved by MLB, that indicates we have a different leadership than we did two years ago. All to the good!