The door is a gimmick used by marketing to refer to them as "suites". The irony of this subpar product is that Delta ran away from DXB and that market claiming not being interested in competing with the big ME3 carriers, yet a few years later try to design a business class product they can call a "suite" with a 9 inch plastic door that doesn't close, terrible food, and hit or miss service.

The true "Suites" on products like SQ, EK etc have about as much in common with the DL product as Deltas food does with a 3* Michelin restaurant.