`_.intersection` operates on sets and as we know from the sets theory in math, order of elements in a set is not important and we must not relay on order of elements. {a, b} = {b, a}

The result of `_.intersection` also is a set and we only represented it as an array, and order of it's elements must not be important.
Why we must preserve the order of first array (set)? Why not preserve the second one? Why not the third?