/clone overlapping is detected in odd ways

The game compares two cuboids from the given coordinates to judge the overlap. However, the two cuboids do not frame the entire selection area for cloning.

for example：
/clone 0 5 0 1 6 1 1 6 0

As expected, the source area is a cube with side length of 2 meters. And the source area overlaps with the target area. But the game does not judge them overlap.

After some tests, I guess that the game detects overlapping as shown in the pictures.

Other examples：
/clone ~ ~ ~ ~ ~ ~ ~ ~ ~
/clone 0 5 0 2 7 2 2 7 0