"Used by" and dependencies not working for Python package

Hello,

I am the maintainer of the following Python package, published on PyPI as “Panda3D”:
https://github.com/panda3d/panda3d

In the setup.cfg and uploaded PyPI metadata, I have clearly defined the name of the package and the association with the GitHub repository via the Source url in project_urls. Nevertheless, GitHub is unable to find our repository when searching for the “panda3d” or “Panda3D” dependency in other projects:

https://github.com/rdb/thingy/network/dependencies

I am not sure at this point what to do to make GitHub recognize the repository as representing the “panda3d” package. It is clearly defined in the setup.cfg file, which is the standard setuptools metadata format. Is the source code of the dependency finder available so that I can try to find out what I need to change to make it recognized as such?