I don't agree. Distutils still uses distutils.sysconfig for configuration information and setup.py wants to adjust that configuration, it should therefore use distutils.sysconfig instead of the global one. 

That said, it would be better to change distutils to use sysconfig instead of its local configuration information (distutils.sysconfig, distutils.command.install.INSTALL_SCHEMES, ...).  That has never been because distutils is frozen due to backward compatibility concerns, but it might be better to actually change distutils for 3.4 when there will be other changes to deal with the new packaging PEPs as well).

However: switching distutils to use the toplevel sysconfig will change functionality, as I wrote in my initial message you can use environment variables to override variables for distutils.sysconfig, but that doesn't work for the global sysconfig because the values in _sysconfigdata are expanded at build time.