On the question of reduction, here is a variation by Elf for a castle game between Honinbo Jowa and Hayashi Genbi on Dec. 26, 1828.
- Click Here To Show Diagram Code
[go]$$Bcm5 Jowa - Genbi
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$$ | . . . O . . . . . . 3 . . . O . . . . |
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$$ | . . . 6 . . . . . . . . . . . . . . . |
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$$ | . . . . 2 . . . . . . . . . . X . . . |
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For

Genbi made the enclosure in the bottom right, then Jowa played in the bottom left corner. The pincer joseki in the top right followed, and then Jowa made the high enclosure in the bottom left.
Elf regards

as an 8% error, and gives the following variation.
- Click Here To Show Diagram Code
[go]$$Bcm5 Jowa - Genbi, Elf variation
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$$ | . . . O . . . . . . . . . . O . . . . |
$$ | . . . 4 . . . . . , . . . . . , X . . |
$$ | . . . . 3 . . . . . . . . . . . . . . |
$$ | . . 2 . . . . . . . . . . . . . . . . |
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$$ | . . . . . . . . . . . . . . . 5 . . . |
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$$ | . . . 1 . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . X . . . |
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$$ ---------------------------------------[/go]
OC, this is thoroughly modern AI play. With no komi, Elf might have recommended that

approach the bottom left corner instead of making an enclosure, quien sabe? But

is a play worthy of Genjo.

Yes, it eliminates any aji in the top left corner, but I don't think we can regard that corner as overconcentrated, and

is a reducing play for the top side. Not that White has a moyo there to speak of, but

lowers the temperature of the top side.
- Click Here To Show Diagram Code
[go]$$Wcm10 Jowa - Genbi, Elf variation, continued
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$$ | . . . O . . . . . . . . . . O . . . . |
$$ | . . . O . . . . . , . . . . . , X . . |
$$ | . . . . X . . . . . . . . . . 1 2 . . |
$$ | . . O . . . . . . . . . . . . 3 . . . |
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$$ | . . . . . . . . . . . . . . . X . . . |
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$$ | . . 5 6 . . . . . . . . . . . X . . . |
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$$ ---------------------------------------[/go]

presses against the top right stone, a favorite tactic of the bots. This is a territory vs. influence exchange. I don't think that we can say that Black is overconcentrated.

, OC, avoids the bottom side in favor of the 3-3 invasion of the bottom left.

Edit: BTW, Elf does not like the pincer in the game,

(another 8% loss), preferring instead the 3-3 in the bottom left.