If you draw a line with 2 break points where the direction the line is going in is randomized and we say there’s a 5° tolerance, the odds of getting 2 right angles forming 3/4 of what looks like a rectangle are (5/360)^2, so 1 in 5184. I don’t know how many formations follow that pattern on Mars and obviously the distribution of angles chosen wouldn’t be uniform, but that’s a very low number. I bet that’s not even the only box-like terrain present on Mars.