Correct me if im wrong here please but a dual outlet plate has the feed or supply in and the ability to connect 2 loads out.Your drawing is showing the highest load on the last point of radial which would be fed by 4mm T&E cable from either a socket or FCU. If the dual outlet plate is fitted then there is no issue with the 2x 6mm T&E cable. One 6mm T&E cable will feed the cooker and another 6mm T&E cable will supply the socket or FCU. By using 4mm T&E to supply the cooker outlet you have a chance that in the future the owner or new owner may install an all electric cooker that will be fed by 4mm T&E and could potentially become a weak link when the electric cooker is under full load.