Take a look at other posts like #208 or #277 at the bottom. The crane's reflection is visibly clear just like clean glass. It's just the angle from where those pics were shot. Nothing but sky to reflect, and the building was shot straight on, so the low deviation in colors and shine in the glass is expected. The photos on page 18 clearly show the normal glass reflection, but Pyongyang has bad air pollution and the pics were shot from real far away so the glass is probably less shiny than I think you're wanting to see.
I think if they clad the thing in a plastic then they would probably already be falling off. Lightweight materials plus winds on the structure near the 1,000 foot mark probably aren't a good mix.