In Benchrest with 36X or higher scopes, sometimes the mirage washes out all the lines on the target. The only thing visible is the black square, due to its thickness. It is now a fuzzy black square, but at least you can see it. I never used it as an aiming point any other time. I adjusted my point of impact to be slightly above the point of aim so I did not shoot out my point of aim.
I used the small center circle as a point of aim. I would center my fine crosshair 1/8 MOA dot reticule in it. In both targets the wind has the group off center, but if it wasn't it would still be above the small circle and leave my original point of aim intact. Unless you are running a fast group in a great condition, one usually did not use the same point of aim for all five shots.
There may have been some, but I was not aware of anyone using the black square as an aiming point at any time other than in bad mirage. The square was explained to me that way when I started. As an aid in bad mirage.
The left group looks like a condition running mostly left while running away a tiny bit as well. The one on the right looks like a condition running away. Judging from my original point of aim.
I do not remember seeing any groups in the black square on the "wailing board".
A nice 5 shot group, and then a heart breaking 4 and 1 group.