Is it natural? Is it caused by weathering?
How about the photo of Mars below taken by the Mars Odyssey by its infrared camera in 2002? NASA tried to pass it off as typical Martian mesas.
Those pics you just posted very well support the idea that the 4-sided feature (”monolith”) is natural, as at least some of the linear features on Phobos (joints, bedding, whatever) ARE at right angles to each other.