Architect here. Adding more glass is not an example of cutting corners. That would be going the wrong way cost wise. Also it's highly unlikely major changes to the facade would be part of a value engineering effort given how difficult it can be to get projects approved and all of the redesign (and fees) that would trigger. Also you can clearly see here in the concept renderings from Perkins Eastman, the architecture firm, the intent was always for the building to dematerialize into glass.

Also here is a quote from Ming Wu, the lead architect on the project:

"Rather than Art Deco, I’d say, if anything, the design is something of a transitional nature. It is very solid at the base with a lot more limestone present in the lower reaches of the building. Stone is a material people relate well to. It has a warmth to it. As you get into the body of the tower, the stone becomes a series of strong vertical linear stone, pilaster lines alternating with glass. Then, you’ll see it next year sometime, as the cladding rises up in the building, at the top upper reaches of the building, it becomes very glassy. The building concludes with a very transparent top, a monumental lantern in the sky. It has a very modern sensibility."

Personally I don't mind the idea I think it's just poorly executed. There needs to be some sort of transition or cornice detail or something rather than the glass just abruptly ending. Also glass is one of those materials that disappears at night so the building looks somewhat decapitated. An office building where all the lights inside were left on would be a different look but residential units are often dark.