How the rule works
One attribute governs another: if the shape is a triangle it is always striped, if the first symbol is a ring the second is always a diamond. The link is the same throughout the matrix, but which value sits where may follow another rule.
It is a rule about pairs, not about direction. It is invisible if you read the row as a series, and only shows when you compare cells that have the same shape or the same first symbol. Two cells with the same condition must look the same in what is conditioned.