Unfortunately, that loco is also meant to be used with a specific face forward as a result, which IR as usual ignored :p
You are spot on (as usual) with your assessment though; the flat profile on rear would lead to lesser drag than the conventional design would owing to closing up of space between loco and coaches. I have added a screenshot from a research paper studying aerodynamic profile of semi trailer which shows lesser vortex formation when trailer truck cab has more aerodynamic profile and less gap between trailer.