N passes out of turn not accepted. Bid reverts to S who is told he can make any bid, but if N cannot make a comparable call to Pass in response, then S must pass at his next turn. You explain the concept and even give the example of say a 1H opening and 2H response or 1NT as being comparable but not a change of suit call, say 1S. All nod their heads. S now opens 2D, alerted and N bids 2H, alerted. You find out that 2H is forced whatever the holding. Not a comparable call you announce (or is it?), and it is likely N/S are now going to play in a silly contract. Obviously S has not understood your explanation and thus the implications of his opening bid.