it's a fact of life that the same
source release may be configured in different ways that create
different resulting dependencies. NumPy is one example of this, but
it's hardly unusual

I've tried to respond to this point twice.. but let me try again. : )

If I'm confused, please help me.

aren't the "different resulting dependencies" non-python, non-pypi system dependencies?

the dependencies the sdist would cover are the python/pypi dependencies, and they don't usually vary based on building extensions

as for representing non-python distro dependencies and build variances, I mentioned before that PEP426 extensions might be used to cover that, but that's still an open question I think..

--Marcus