'Game Changer' PGN Explored

Last month, in 'Game Changer' PGN, I collected PGN files relevant to Sadler & Regan's book 'Game Changer', and noted,

As a bonus, the 'Annotator' tags in the NIC file match the 'Round' tags in the AZ_vs_SF files. This provides a cross-reference between the two sets of files. I'll use these files for further explorations.

The 'NIC file' is a PGN file covering the games in the book. I used the NIC file to prepare last week's post, Playing Without a Horizon. The 'AZ_vs_SF files' are two PGN files of games between AlphaZero and Stockfish provided by DeepMind to Sadler & Regan. Those games were behind the authors' motivation to write the book.

Having a little time on my hands, I used it to dig deeper into the three files. The 'NIC file' contains 106 games in the same sequence as the games presented in the book. Of these, 69 games are AZ_vs_SF, while the other 37 games are from various sources. Many of the other games were played between world class players and were used by Sadler & Regan to illustrate recurring themes from the AZ_vs_SF games.

Of the 69 AZ_vs_SF games, 48 have AlphaZero playing White. One peculiarity of the 'NIC file' is that only 51 of the 69 games can be cross-referenced to the AZ_vs_SF files. That means 18 games are from other sources. I looked at the first two of those games (no.12 and no.17 in the NIC file) and confirmed that they are indeed missing from the AZ_vs_SF files, although they are discussed in the book. Were there other game files examined in the preparation of the book?

Of the 51 games from the AZ_vs_SF files, 32 are unique, meaning that many of the games were used more than once in the book. One game appears four times. By some sort of pleasant coincidence, this is the same game I discussed in last week's 'Horizon' post.

Despite the massive effort that went into Sadler & Regan's book, there are still plenty of the original AZ_vs_SF games to explore. What other chess secrets might those games reveal?