yes. It takes Beta0 as an input (no angular correction applied at all) and removes the impact of both the global (ellipsoid) and local (topography) incidence angle. An explanation is given here: Radiometric & Geometric Correction Workflow - #71 by ABraun
This checkbox is a leftover from ealier stages of the software. The developers decided to leave it in in case someone is using it in operational workflows, but its functionality has been replaced by the Terrain Flattening operator. Additionally, it seems to have little effect on Sentinel-1 data. We had discussed this here, please have a look at lveci’s answers: S1 radiometric correction - #2 by lveci
Best greetings to Jena by the way 