This complex is not built in rock. The material looks like soft sediments or even sand dunes. Rock can be seen in the lower right-hand portion of the photos showing the dam. The striations are steeply dipping (tilted) rock strata. The rock lies not too far below the soft sediements so tunnels may go down into rock.
The camp location next to the reservoir is very clever. It gives the occupants an unlimited supply of water by simply drilling wells in the rock down to the reservoir level.
The article does not identify the corral-like structures and round bunker just left of the dam. These appear to be fortifications to control any invaders who would cross the dam - the only road access to the site. The area is protected by the river and reservoir, as well as the steep terrain of the river canyon.
The numerous tunnel entrances identified look like small bunkers, probably to hold explosives or ammunition. There is no road access to them. Vehicles would have to drive up the dry wash to reach them. While relatively flat, dry washes often have soft sand that bogs vehicles down. No recent tracks are visible. These bunkers would also be inaccessible to vehicles following flash floods.
The identified helipad is too large to have only that purpose. It is nearly the size of two football fields. The material is probably spoil from a shaft that goes down into the tunnel system from the ridge top. By measuring the volume of this material (using stereo photgraphs) the volume of the excavation can be estimated.
U.S. intellegence can go back in their files to check changes in this area over the years. That will give them a good idea of how the site was developed and what the functions of the various areas are.
Overall, it looks very crudly and haphazardly built. The fact that it is excavated in soft sediment may indicate a very unskilled manual labor force, with no ability to excavate the hard rock in the area.