FWIW, I regularly rely on using specs like numpy>1.0.0a1 (not specifically for numpy, but since it’s the current example…) as dependencies when I need to rely specifically on a prerelease version. Often in a pyproject.toml to use a prerelease backend, so there’s no other way to specify that it should be a prerelease right now.
I guess if numpy>{largest non-prerelease version} would find a later prerelease until there was a non-prerelease to find, that would also work, arguably better.
But I don’t think a command-line option sufficiently covers the scenario, at least not without changing vastly more tooling than just pip.