He's doing that because he's Mac-like. HIs hips and shoulders are square - he just drops the right foot back a little. Mac does that for both of his patterns, IIRC. It's important to note that your feet can be set one way while your hips and shoulders are set another way. Like Zach, like Mac, and like other people whose names don't rhyme.
I often find it easier to hit a push-draw with an open stance. My body senses that the target is "out to the right" a little and will swing out in that direction more. Some people do as you do - they swing more along their body lines.