Craters are 'supposed' to be round, which is why Hoagland sees inner Buksminster Fuller structure in Iapetus. If a crater has straight sides, it must be something in the underlying terrain that gives preferential direction to the excavation. Fault lines would do it.
I am not as ready to accept that the meteor landed right smack dab in the middle of a set of fault lines laid out on a checkerboard square pattern.
One fault line which would produce a distorted circle, or two parallel ones which would produce a distorted oval I could accept, but the symmetry of the square pattern is very great. A hit somewhere other than in the middle of a square (very, very rare) geologic formation would be expected to produce a crater of a different shape.
I can not think of any other square geologic formations on that scale anywhere on earth--can anyone else?