Health app distance accuracy

My wife is short, and I am 9” taller, so we know our step count will be different. Our distance data is also vastly different, with no apparent reason. The latest example today is we walked the exact same path through a town. We never left each other’s side, and our iPhone Xs were with us. The results were: 20,799 steps for her, 16,272 steps for me; and 8.7 miles for her, and 5.7 miles for me. How does that make sense?