'Radiological union lags behind clinical union' is what they taught me. In other words, what you see on the X-rays lags behind what's happening with the fracture's healing.
This is because the union is fibrous material which gets calcified later.
I suspect it may take up to a year for mature bone to bridge the gap on X-ray. It is unlikely that the bone will reshape to its original form. This does happen with kids and after surgical repair.