While pretty neat, they look like they're just extra resources/builds that weren't used. The MAC is probably something they were playing around with but tucked away. If you believe the Kotaku article, then you'd know that the toolset to work on Destiny absolutely sucks so it would probably be easier to tuck things away than delete them.
English
-
Yea I think it was tucked away a rough initial build for the raid
-
Or, did it occur to you that it might be a valuable, important zone later on? Next DLC, or somesuch? After all, the King's Watch area sat unused for two DLC's before becoming an area we would be seeing.