He's a pussy bitch. He knew it wasn't 50/50. This place means the world to him therefore he came up with rules that fit him....GB can always go elsewhere.....therefore he took Justine's offer knowing this guy is usually always wrong about everything
And GB accepted the bet and had the advantage. GB's accepted bet had a far greater chance at winning than the one-on-one contest. Mob is too dumb to realize it.