For your information, another use case where the current situation is inappropriate : I am running windows but trying to download macosx and linux packages. This fails with pip download because of the build step.
To give more context, this is for the PyQt5-stubs projects. The PyQt5 wheels and source distribution include some platform specific stubs and modules. Since I am distributing one set of stubs for all platforms, I want first to collect all stubs from all platforms by downloading all packages. And this fails…