When using tricks which can slow ones fall, such as add motion do nothing to help negate fall dmg

heres my basic spell:
{spellName:"Add Motion",uuidMost:7087621840040509788L,validSpell:1b,spellList:[{data:{key:"constantNumber",constantValue:".25"},x:3,y:3},{data:{key:"selectorCaster"},x:4,y:2},{data:{params:{_direction:4,_speed:3,_target:1},key:"trickAddMotion"},x:4,y:3},{data:{params:{_x:0,_y:4,_z:0},key:"operatorVectorConstruct"},x:5,y:3},{data:{key:"constantNumber",constantValue:"1"},x:6,y:3}],uuidLeast:-5293915898338595390L}

I used it on the pants
It seems to just be based off of maximum hieght to ground contact point, as if you fell at nomral speeds

That is vanilla, it deals damage based on fall height, not motion.