What I have always noticed is the similarities in both the pitching and hitting motion. In order to both throw and pitch hard, the core area of the hips must wind up against a stationary rear foot. This causes the back at the shoulder area to wind up slightly more than the rest of the trunk. From this point the body acts like a catapult with the lead leg acting as a counter weight to help drive the loaded force forward and then being planted to act as the force keeping the weight from falling into the ground. The lead leg and foot must come planted in a fairly open position to allow for proper hip rotation which precedes the arm motion into catapult forward motion. The arm is then catapulted forward forming a perpindicular line with his body trunk at release. the way the lead leg moves initially really doesn't matter whether it sweeps or it is more linear as long as good balance can be maintained before and after foot plant. Both batters and throwers will either be linear or sweep into a slighly open position. Sweeping into a slighly open position helps the hips rotate quicker and more degrees in my opinion because it allows the hip more unhampered movement which allows the leg to follow a more natural path leading to more usable power and less injuries.
In batters they don't like them to open up to much because you lose the ability to hit outside pitches. I compensate with just standing closer to the plate or begining slightyl closed.