When I use --Vec2/3/4 for script arguments (I want nice neat input tables) the default value of the first element is always over-ridden and set to 0.0
Script.TestThis = { 1.0, 2.0, 3.0, 4.0 } -- Vec4 "testing"
Will offer up 0.0 2.0 3.0 and 4.0 as the default values.
Same behaviour with Vec2 and Vec3