Black has already the first move for reducing White's upper right corner.

Instead of following Black with for an early Guzumi-Exchange, White blocks the Hanezeki's Tail.

The Jûrokubango has come to an end.

Until the Jûrokubango (bold section), Black's Initial Self-Play Success Ratio (the blue line in the diagram) stabilised just over 45%.

During the Jûrokubango, it fell sharply of its own accord. Ultimately, it stabilised in the critical range (below 20%).

28b's surplus of won games in the Jûrokubango (the red line in the diagram) was in the range of -10 to 0, showing an upward trend. This makes sense in that both 28b and 40b won most of their games playing White.

So we are looking at a "false positive" here !

Please click the board for SGF-download ...
(28b = Black)

Please click the board for SGF-download ...
(28b = White)

The comments indicate the number of games in which the respective variation was selected.
E.g. "A=19 // B=264" == Variation "A" was played in 19 games, variation "B" in 264 games.
(The labelling is designed for SGF-editors that label next moves with capitals "A", "B", "C", ...)