After 30 games the score is 4-4 with 22 draws. After 8 consecutive draws Leela won a game pair and evened the score. So far the draw rate is high compared to previous superfinals, also higher than the expectations of the book makers (according to chat comments by Jeroen Noomen). Apparently the newer versions of the engines are able to hold against bias that was high enough for a win 6 months ago, when the book was created.
Games 21-22 started with a sideline of the Budapest defense, Rubinstein variation, still in human chess theory. White was a pawn up, both queens moved forward, the white queen in the center and the black queen on the queen side. In game 21 the black queen retreated after a while and both engines castled short. The engines mainly played behind their pawn lines and there were only a few minor piece exchanges. Stockfish pushed a pawn to a3, the game reached a QRN vs QRN position and on move 55 the engines started to shuffle. The engines exchanged rooks and continued to shuffle, the game was adjudicated on move 123 when Leela's eval was low enough. In game 22 the black queen kept its forward position on the queen side. Stockfish left the black queen alone and focused on the king side. Stockfish traded both its bishops for knights, evals came down. Leela captured two pawns on the queen side and created a passer, Stockfish reduced to a QRN vs QRB position and created a passer in the center. Leela pushed a passer forward and Stockfish attacked the black king. Leela queened and Stockfish threatened mate, the game was adjudicated but the PV showed Leela had to give back a queen, resulting in a drawn queen ending.
Games 23-24 started in a sideline of the Blackmar gambit with black a pawn up and a bias for black. After trading a pair of minor pieces Stockfish attacked the white king and forced it to move. Stockfish completed developing the queen side pieces and Leela moved its queen to safety on the queen side. Stockfish captured a second pawn, evals came down as the engines shuffled for a while. Leela got a pawn back and after a series of exchanges the game reached a RBN vs RNN position. Evals were close to 0 as the engines mostly shuffled, the game was adjudicated in a rook ending with equal material. In game 24 the engines repeated the reverse game for 16 plies. On move 19 the engines started to play out a long PV agreement, Leela captured two more pawns, it gave a rook for a knight and the engines exchanged queens. During this PV agreement Leela's (negative) eval drifted down but was still around 1, Stockfish's eval was stable except for two spikes that lasted one move each (exciting or alarming, depending on whose fan you were). The game reached a RRB vs RBN position with black 3 pawns up and a passer on the king side. Leela's eval increased over 1 for a while, but after exchanging a pair of rooks it came back down. Leela captured a 4th pawn and created a passer on the queen side, Stockfish moved its rook to the 7th rank. Leela gave a pawn back, soon it was out of pawn moves. The black king could not move forward to assist its pawns, evals came down and the game was adjudicated.
Games 25-26 started with a 4 ply book in the Nimzowitsch defense. In game 25 the engines developed their pieces without exchanges after the start. After move 16 there were a few pawn and minor piece exchanges, the queen side opened and evals came down. There was a period of mostly shuffling, and then a series of exchanges reduced to a QRR vs QRR position with white a pawn up. Stockfish pushed a passer to the 7th rank, Leela reduced to a rook ending and captured the passer. Evals were close to 0 and the game was adjudicated. In game 26 the engines opened the d file and castled in opposite directions. Stockfish pushed pawns on the king side and Leela on the queen side. After a series of exchanges the game reached a RRN vs RRN position and evals came down. Leela pushed a passer to the 2nd rank, Stockfish gave a rook for a knight to capture the passer. Evals were close to 0 and again the game was adjudicated.
Games 27-28 started with an 18-ply sideline of the KID Orthodox variation. In game 27 the engines castled in opposite directions, Stockfish captured the h pawn and Leela doubled rooks on the half open h file. Stockfish kept the h7 pawn safe, evals came down as exchanges opened the center. A series of exchanges reduced to a RB vs NN position with black two pawns up, Leela's eval came down enough for adjudication. Game 28 repeated the reverse game for 18 plies, Leela kept the h7 pawn safe as before. The center remained closed, Stockfish took the time to send a knight from f3 to c2 in 4 jumps. After Leela moved pawns on the queen side Stockfish jumped with the same knight to c6. Evals slowly came down, after a few exchanges the engines started to shuffle. Close to the 50-move draw the engines exchanged queens and continued shuffling. Evals were close to 0 and the game ended in a repetition.
Games 29-30 started with a 28-ply book in the Ruy Lopez, Chigorin defense, Panov system, a line rarely seen in recent human chess. The center was blocked and the c file was open. In game 29 the engines opened the a file and then exchanged all the major pieces quickly. On move 28 Stockfish thought for 11 minutes, then it deviated from the agreed PV and its eval jumped, Leela's eval jumped as well. The engines opened the king side, after a while Leela captured a pawn on the queen side and created a passer.
Stockfish's defense collapsed, Leela captured the last black pawn and had 3 connected passers. Stockfish could not stop the passers, eventually Leela queened twice and mated.
In game 30 the a file remained closed, the engines exchanged a pair of rooks through the c file but the other major pieces stayed on the board longer than in the reverse game. Evals came down slowly, Leela attacked the center from the king side while Stockfish focused on the queen side. The engines cleared the pawns on the queen side and Stockfish moved a rook forward. Stockfish gave a knight for two pawns and created a central passer. In a series of exchanges Leela gave back the material and captured the passer, the game reached a RBN vs RBN position with white a pawn up. Evals were close to 0, the game was adjudicated in a drawn rook ending. Leela wins the game pair, the score is tied 4-4.
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