bdist_wheel makes absolute data_files relative to site-packages
bdist_wheel doesn't handle absolute paths in the "data_files" keyword like standard setuptools installs do, which honor it as absolute (which seems to match the examples in the distutils docs)
when using absolute paths, the data ends up in the packaged wheel at the top level, and get's installed relative to site-packages (along with the project packages)
so, bdist_wheel is re-interpreting distutil's "data_files" differently. maybe better for wheel to fail to build projects with absolute data_files, than to just reinterpret it.