Why does Si perceive the object as a whole?
Any sensor type will focus on the details of the car - the colour is red, it takes up a lot of space, surface looks shiny, textures etc. Si specifically would be the focus on comfort, how the seating feels for example. When you just the car seat's distance to the wheel, or you go in the car seat and feel your legs are too close/far from the pedals, you're using Si.
Si and Ne are the complete opposite, and recognising the car as an object vs recognising the objects potential aren't quite the opposite things as both are objective.