Setup requirements not consistent

I tried downloading pynacl and all the requirements with pip3 download which downloaded the following packages: pynacl, six, cffi, and pycparser (required from cffi).
However if I bundled these packages and moved to a machine that did not have internet access and tried to install (via pip3 install --no-index -f <package_dir> pynacl) from the local wheels it will fail because the install requires a different set of packages: setuptools, wheel, and cffi.
I am assuming from the comment in the pyproject.toml that the issue is the setup_requirements in setup.py don't match (they are empty in setup.py).
I also think it is strange that the pip install command is passing the --ignore-installed flag because I already do have setuptools and wheel installed but it is still trying to find the packages which it can't when not connected to the internet.

Compare setup.py's setup requirements with the comment in pyproject.toml, then reproduce the reported pip3 download and offline pip3 install --no-index -f <package_dir> pynacl flow. Done means the declared requirements are consistent and the bundled packages install successfully without internet access.