This is part of White's plan. The combined piece and pawn attack  is most powerful.
1. g1f3  1... c7c5  2. e2e4  2... d7d6  3. f1b5  3... c8d7 This is considered the safest continuation against the Moscow variation. 4. b5d7  4... b8d7  5. e1g1  5... g8f6  6. f1e1  6... a8c8  7. c2c3  7... e7e6  8. d2d4  8... c5d4  9. c3d4  9... d6d5 Modifying the structure to a French one.  In return for the tempo wasted on d7-d6-d5, Black can brag about swapping  his poor light-squared bishop. 10. e4e5  10... f6e4  11. b1d2  11... e4d2  12. d1d2 A cool  move! It had already been played in a game which apparently was not  overlooked by the world champion. 12... f8e7  13. d2f4 The point behind the capture. White's pawn chain  highlights the kingside, and this is where White should be attacking. 13... e8g8  14. f4g4  14... f8e8 Xiong frees the f8-square for his light pieces, and this turns out to be a novelty.