comment: Probably an indication that Abdusattorov was playing for a win. In the main variations with 4...0-0, the theory is very developed, and it can be difficult to find an idea to unbalance the game.
context: 1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. b1c3  3... f8b4  4. d1c2 One of White's most solid options against the Nimzo-Indian.