The Diamondbacks’ performance in home games put them above 500. Through 31 July, the Diamondbacks won a lot at home (31-25), while their away record was near 500 (27-26).
Are runs scored and runs allowed fails to explain why they did better at home. Through 31 July, at home they allowed 11% more runs per game while scoring only 5% more runs per game (compared to away games).
So, why the better record at home? The answer is 1-run games. Through 31 July, in 1-run games, the home record is 11-5, while the away record is 7-7.