What does it mean that `toString` gets “ignored” if it returns a non-primitive?

Question

The MDN documentation on Object.prototype.toString says that when toString gets overriden, it should only return a primitive value:

The toString() function you create must return a primitive, otherwise it will be ignored.

However, in the following example we return an object inside of toString and it returns the object normally:

const ob2 = {
    val1: 100,
    val2: 200,
    toString: function() {
      return {
        veh: "meh"
      }; // Object.
    }
  };

console.log(ob2.toString());

Output:

{ veh: "meh" }

So the toString method returns the object normally. What is up with the misinformation?