As far as I’m aware, there isn’t a way to control the cut as you would like. You need to be aware that, depending on how they were drawn, each edge of a square has it’s own line, so even though they may appear as one, because the shapes are overlapped, WAM will see two lines to cut.
One option is to draw the shape so the two internal, vertical lines, are slightly shorter, so they don’t touch the large outer rectangle (perimeter). This way the two vertical, internal lines will be cut first and then the outer perimeter will cut-out the 3 squares.
There’s a few other topics discussing WAM control that might help. Here’s a few: -