bg_mesh not working

[Nick20500]

I'm using fTetWild to create .msh files from .obj files. My Objects are composed of several segments which I later "glue" togehter in a physics simulator. For the processing of glueing the parts togehter (e.g. connecting the body of a bottle with the cap) I need to retain alot of vertices. While I want to coarsen the mesh every where else as much as possible to make the simulation faster.

For that I created a bg-mesh which I then pass into fTetWild when creating the .msh file.
But it seems, that the bg-mesh isn't working properly. In the Image down below you can see the orange and black grid of the bg-mesh, which is i circle where the bottle cap would meet the bottle body.
The diffrent colored triangles is the result fTetWild gives me for meshing the bottle body.

Why is the bg mesh not doing anything to the mesh result? I expect in the resulting .msh file to be a cicrle of smaller tetrahedras where the bg-mesh is.

Here is the command I used to create the volume mesh for the bottle body:
./FloatTetwild_bin -i "bottle_body_unioned.obj" -o "uncoarsened_obj_coarsened_mesh_with_bgMesh_bottle_body.msh" --smooth-open-boundary -l 0.9 -q --coarsen --no-binary --manifold-surface --use-floodfill --bg-mesh "output_bg_mesh_bottle_body_22_ascii.msh"

Here is the zip-folder with all the used files: fTetWild_issue_example_files.zip