These passages do not make precise distinctions between these terms-certainly not precise enough to define metaphysical components of human existence. Scripture typically uses "spirit" and "soul" interchangeably.Systematic Theology: An Introduction to Christian Belief (Kindle Locations 21024-21026). P&R Publishing. Kindle Edition.
If my understanding is correct, then both the procession and the sending mentioned in the verse take place in history. Now, that understanding does not make the verse irrelevant to the doctrine of eternal procession, for as we have seen it is legitimate to find an analogy between the historical and the eternal relationships among the persons of the Trinity. But if both the procession and the sending of John 15:26 take place in time, that would support, by analogy, the view that the Spirit's eternal procession is from both Father and Son.Systematic Theology