Apparently, the French GM realized what he had done and this  move came after almost 12 minutes of reflection.
1. g1f3  1... g8f6  2. c2c4  2... c7c5  3. b1c3  3... d7d5  4. c4d5  4... f6d5  5. e2e3 Vachier-Lagrave has a lot of  experience in this Anti-Gruenfeld. 5... d5c3  6. d2c3  6... d8c7  7. e3e4  7... e7e6  8. f1d3 A novelty, which should have been  anticipated by the French GM. 8... f8e7  9. d1e2 Now it is some sort of Alapin Sicilian, where Black  should be careful about the possible kingside attacks as he is missing his knight on f6. 9... c8d7 Intending Bd7-c6 and Nb8-d7. 10. e1g1  10... e8g8 A very careless move. 11. e4e5 