@icekatze Generally longer legs mean that your stride (the length between your steps) is generally longer than people who are shorter. It doesn't mean that you'll be "Faster" as people walk at different paces but it can be an advantage in running if you train.
Whoever created this system is literally reaping what they sowed. The world literally encourages the summoned hero to murder and they expect not to inevitably (out of how many hundreds of heroes they've produced) create a sociopath.