The lead makes a “small” difference
Alan Bennett, an English playwright and actor, said, “We started trying to set up a small anarchist community, but people wouldn’t obey the rules.”
The defenders have a much harder job than declarer. To try to balance the books, the defenders make the opening lead. Often that can make a difference of one trick, but occasionally the number is surprisingly high. Look only at the West hand. You open two spades, a weak two-bid. After two passes, South balances with two no-trump, and North raises to three no-trump. What would you lead? We all know about fourth-highest from the longest and strongest, and that might work well, if partner has two spades, gets in before declarer has taken nine tricks and pushes his remaining spade through declarer’s holding.
Here, though, it is a disaster. South wins with his low spade, plays a diamond to the board, takes two club finesses and collects the first nine tricks via one spade, five diamonds and three clubs. Now let’s go back and have West deduce that dummy does not have four or more hearts, because he made no attempt to uncover a heart fit. If West leads the heart five, how many tricks can EastWest take? A heart to the jack, a spade to the nine and 10, a heart through and a second spade at trick seven give the defenders five hearts and six spades for down seven!
Finally, note that if East were in four hearts, after South leads the diamond ace, North should signal with his queen. Then South continues with a low diamond for the killing club-queen shift.