Looking the edge traced version of the now famous photo, I cannot see any alteration, nor compression artifacts.
All the contour lines in the blurred area are in line and linear with the rest of the contour. It is just darker, so I'd say that the blurring is because there is sand/mud flying over the central area, perhaps because the ROV has moved the box a bit to see if the CSMU is there or not. Definitely not because of any alteration.
