Its a thoughtful reply, however if you insist that theism must address the question of physical creation, then you are insisting upon a tangible, visible God along with presuppositions about reality. If you believe (as John seems to) that you become increasingly real as you become more righteous then you have a sliding scale for physical reality. The concept of false realities is an ancient one and occurs in multiple cultures. People think about it all the time. Its also debated in Physics as people continue to question the nature of reality. Its what people do, so it should not surprise.I'm not sure I would say "non-ontological", but rather (perhaps) that John presents an ontology of the spiritual rather than the physical. "God IS a spirit"..."I AM not of the world"..."glorify thou me with thine own self with the glory which I had with thee before the world was"..."Before Abraham was I AM"..."that they [Christians] may be one, even as we are one"...etc. God, Christ and Christians are all ontologically established as part of the realm of the "spiritual". But even in these quotes the reality of "the [physical] world", and the undeniable fact that even the most "spiritually-inclined" and "faith-filled" Christian cannot possibly avoid having to live in the reality of the physical world, is not denied. Indeed, even Jesus himself seems to grapple with this issue in prayer in Chapter 17. So I don't think, on balance, that John (or John's Jesus) is really "entirely unconcerned with the physical world". He might not have much to say about how it came to be, but taking that as meaning it (the reality or the subject of physical creation) was/is not important is a bit like saying that (the reality or the subject of) physics is not important because it is not mentioned much in Russell and Whitehead's Principia Mathematica. Of course the spiritual realities are of great importance to theism, just as the principles of mathematics are to physics, but a theism that declines to address the question of physical creation is surely as deficient as a physics that declines to address the question of the origins of the physical universe. We might not have pat answers - but we can't just bury our heads in the sand and pretend there isn't even a question.
My point here - and I may have overstepped the line in a non-debate forum - but I think it is a fair question - is this: how complete is a theism that does not address the question of how the physical world came to be?
Catholics often believe that they are leaving this world and moving towards heaven as they approach eucharist in a church. Neopagans have 'Sacred spaces' which are places with an altered reality. Buddhists very logically ask what is real and whether this world is a dream. It is quite common for people to question physical reality. You can be a theist and not care about the creation of this physical appearance if what you care about is the creation of something else -- like some kind of sacred space or existence.