Based on the following photo of alpha prototype (from MotoTrend photo session) there are three panes of glass: windshield, top section right above first row, and long section covering second part of the roof above second row and continuing as a rear view window:
So the metal roof is possibly means just the second part only. I.e. the long part of glass on the back will be the same for all-glass roof and metal roof configuration. Hence no hatchback for metal roof option.
It's just my guess however. I don't remember any pictures of RCs with metal roof