Not understanding the objections. These glasses are a display, right? There's a computer in between ultimately responsible for what the eyes see. With enough clever processing of the scene, why wouldn't you be able to achieve this?

The glasses are not a normal display. Most displays are opaque, and can display pure black by simply not emitting any light. These glasses are transparent, so when they don't emit any light you see whatever's behind the display, not black. Displaying true black on a transparent display requires an extra element which can selectively block incoming light. These glasses don't have such an element, and cannot display black or dark colors unless you happen to be looking at a black object in the real world.