How to Avoid a Balanced 9-card Fit

K
Q 9 5 4
A Q 8 7 2
A 3 2
A 4 Q J 10 9
8 6 J 2
K J 10 6 5 9 4
10 6 5 4 Q J 9 8 7
8 7 6 5 3 2
A K 10 7 3
3 Opening Lead: 8 of hearts
K Vul: E-W

WestNorthEastSouth
Pass 1 Pass 1
Pass 3 NT Pass 4
Pass 4 All pass
WestNorthEastSouth
Pass 1 Pass 1
Pass 1 NT Pass 4
All pass
How do you keep away from a healthy 9-card balanced fit with all top honors except the J in favor of an unbalanced 7-card fit where you have only one easily captured honor. Well, I found (equally inexplicable) ways. Only the first involves a preference bid. South bids spades, then hearts and dummy, looking at powerful support in the latter and lone king in the former, opts for -- opts for . . . the suit where he has a singleton! Incredible.
The second bidding sequence is even harder to understand. With six-five in the majors, with a puny 8-high spade suit and a powerful second suit, a five-carder, this bidder chooses not to mention the powerful second suit! It makes no sense. It simply makes no sense.
In the play of the hand, forgetting what the defensive hands look like, which suit would you like to exploit: the 6-1 or the 5-1? And the answer has to be . . . the former. You've got 6 diamonds (combined) and 7 spades. Can you set up the suit? It looks to me as though you can if you hop to it right away. Win the heart lead, lead a spade, take another heart lead and ruff a spade, come to the K of clubs and ruff a spade. That's dummy's last trump, but what of it? You got three spade leads in. Come to the closed hand with a club ruff or a diamond after cashing the A and lose a spade to East, and since you still have two trump left in the closed hand, you obviously have an entry to the established spades. Don't bother to cash the A of clubs. It's now redundant. That 4-2 split in spades is the most likely with 6 cards out.
In a spade contract, the defense has four quick spade tricks! And I thought I had it bad when a partner preferred spades over hearts with 3 of the former, four of the latter. I just don't understand how anyone could prefer spades here with a 4-to-1 disparity.