I was comparing the results of Range Doppler Terrain Correction with an internal 10m DEM, including local incidence angles outputs, between a descending and an ascending pass, near dates, testing the attachment/detachment of GCP Geocoding in the operation. I noted that the local incidence angles, for the different passes, were aligned! The backscatter for the two passes display the previous observed displacement, with or without GCP Geocoding.
This can be part of the explanation for the artifacts that appear at very steep terrain ridges and streams/valleys, on Radiometric Terrain Flattening, as observed in this post: