That's what I just said happens... then you turn around and say it. And it's contrary to your own logic in the op. I'm not sure if your grasp your own point. How something is understood, be it God, evolution or 1+1 doesn't actually have an effect on the "something" as it's existence is not dependant on how people's understand it and if it does then it's a myth.
Santa Claus can be traced back to an origin point and prior to that point there was no Santa Claus so Santa Claus as we know him today is dependant upon the origin point and evolved story and thus is a myth or more specific a legend since he was a real person in the 4th century.
We could arguably say God is dependant upon a origin point of every people group that has ever existed and will exist. They are varied and conflicting interpretations of God spread across time since history was recorded and have evolved and continue to evolve.
But are we saying pre-history there was no concepts of God? Like saying pre-Saint Nicholas of Myra there was no Santa Claus? No we can't say that because we can responsibly infer that concepts of God predate history itself so the converging origin account is untraceable even if some myths are and so cannot be used to broadly point to a myth/legend of God himself. Certainly the varied accounts tell us evolved myth/legend were happening but still there is no traceable origins and it would seem concepts of God abstractly are developed independantly of outside influence.
Why do all people ever, and who will ever be, regardless of their conclusions, ask the question is there a God since there was ability to think that question? It would seem God predates the question itself.