Well interestingly, in the standard blub on the VW website (not in the brochure), it does say the following when looking at the GTI headline details:
Differential lock
The optional front differential lock and progressive steering, (which is fitted as standard), make driving on winding roads in your Golf GTI even more enjoyable. For enhanced driving dynamics, better traction and more direct steering control.
But if you look in the new pricelist under options, there's no mention of a differential lock option ? Maybe it's coming later and rather than opting for the performance pack, now the new GTI already has the increased power as standard, maybe you will be able to add the electronic differential lock as an option soon ? Then the only thing that is missing is the larger brakes with the "GTI" logo calipers ?