I understand it perfectly.
But if you think a vaporized truck that's spread across the galaxy can still haul brush, or an arm that's vaporized and spread across the galaxy can still lift a cup of coffee, you've taken leave of your senses.
It doesn't matter that "the interactions between the particles remain functionally equivalent".
Once you spread my exhaust system's particles across the galaxy, they cease to be usable for the work they used to do. Ditto for the spark plugs and pistons.
That's because they no longer form the object which they used to form which was able to do the work it was able to do in the world.
The fact that the particles are still dancing in relation to each other by magic doesn't change that.
ETA: I'll give you a choice... I'll either fire a bullet at your chest with my Ruger, or I'll fire a vaporized bullet at your chest (consisting of particles spread across light years which are behaving, relative to each other, the way the particles in the non-vaporized bullet are behaving). Do you have a preference?