That’s an excellent question. Your question reveals that you have read Chapter 4 of “New Proofs,” which deals with Lonergan’s proof for God’s existence, and your question logically flows from the possibility left open by Lonergan because an unrestricted intelligible reality (UIR) could have created a creator of our universe.
Lonergan’s proof shows that the UIR must be the ultimate creator of all that is, however, it does not say that the UIR has to be the proximate creator of our universe.
It only has to be the ultimate creator of our universe. Are there other creators in between? There could be, but if we operate by Occam’s Razor (the assumption that the most elegant solution with the least number of assumptions is the best one until proven otherwise) then we might assume that the UIR is both the ultimate and proximate creator of our universe.
Longergan has shown that there has to be one and only one creator which is at once timeless, and unrestrictedly intelligible.
I think Lonergan has proven this quite well in his book “Insight: A Study of Human Understanding,” Chapter 19.
He has asked anyone in the intellectual community to critique his reasoning and has been met mostly with silence.