It sounds pretty simple.
SCU-Mt.P does all the top players (U10 and up....Select and Academy are the terms used these days) and Mt P. does all the rest of the levels. Basically, two separate entities but the words "licensing agreement" applies for the ability for SCU-Mt.P to use the MPRD's fields and so folks don't think there's big changes, even though there is, and freak out. Essentially, it's a merger without folks using the terminology to admit it and keep civility.
But, a great step for the top players and something that has been a long time in coming for the Lowcountry. Add in a few more of the other Lowcountry entities still trying to do their own thing and this area is in business.