If a product doesn't have geocoding information, it is useful to use the GCP Manager to define GCPs and then attach the GCPGeocoding.
However, after saving the product to dimap and reopening it, the geocoding is lost (or not attached).

If a product has been saved with an attach GCPGeocoding then it should be read with it attached automatically. This way, GPF readers will read a product with a usable geocoding.

Thanks
Luis