Question 1. Does the RasterizeTerrain setting in the RecastGraph mean that the terrain is rasterized and included in the scene file?
Or does it mean that it will be included in the graph file?
Question 2. Is the reason for rasterizing the terrain and including it in the scene to be used to regenerate graphs in runtime?
It means the terrain will be taken into account when scanning the graph. Otherwise the scan will completely ignore the terrain.
The result (a scanned navmesh) will be included in the graph file, if you have one of those.