I don't get this one either. RB1 wants you to keep 9m to give yourself an opportunity for ittsu. That much I can understand. However, I don't understand its advice to cut 2s. By cutting 2s, you're going back in shanten because you're turning your finished 567m block + floating 9m into two unfinished 56m and 79m blocks. Wouldn't it be better to treat the 9m as a floating tile and just cut 6p (or 8p, but 6p seems better to keep two heads)? That way you'd make the pinzu shape weaker, sure, but you wouldn't go back in shanten, and you could still cut the floating 9m if you reached tenpai without completing ittsu.
My real question is why is it ok to go back in shanten in these two examples.