different bindings have different amounts of forward lean when set to (0) I had some old technines and burtons that had way to much lean when set to Zero and had to remove the flad to get the right amount
highback flex has a lot to do with it too, I'll set a softer highback up with more lean then a stiff one, because the soft one flexes back with initial contact. I have metal highbacks on my bent metals and they dont flex at all meaning i run less lean and get the same response. Too much lean with some highbacks will cause calf bite depending on the boot, also it makes you look like your taking a poop while you traverse heelside.
splitboard bindings (sparks and kara's) go past 0 to around -10 degrees to allow more freedom when touring, if you ride them in that setting you will notice the lack of heel side power.