Since the  knight on d4 is loose, this is perfectly possible. Caruana is trying to  obstruct the comfortable development of the opponent's dark-squared bishop and in the meantime gains more space for his pieces on the queenside.
1. c2c4  1... e7e5  2. g2g3  2... g8f6  3. f1g2  3... f8c5 So revealed that he was somewhat surprised  by this opening choice by Caruana. 4. d2d3  4... c7c6  5. g1f3  5... d7d6  6. e1g1  6... e8g8  7. b1c3  7... a7a5  8. d3d4  8... e5d4  9. f3d4 