I think the plan is to clarify the respective roles.
The sectional ADCs are there to support/assist the DC, and not to try to manage the sections operating within the Groups. As I understand the changes, the purpose is to clarify that section leaders (in fact all adults in the Group) are 'managed' by the GSL. It is the GSL, therefore, that needs to know what the sections are doing, and provide support as required, not the sectional ADCs.
I suspect some of the current sectional ADCs will take on GSL roles where the DC is (by default) the defacto GSL.