The bishop is developed on this unusual square, without Black needing to worry about the move Bc1-g5, if I understood correctly the idea of the move h7-h6.
1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. g2g3  3... d7d5  4. g1f3  4... h7h6 A mysterious move that seeks a slightly different piece development than what we normally see against the Catalan Opening. 5. f1g2 