If this magic of multiple interfaces in "provides" was real...
<genericsetup:registerProfile
name="uninstall"
title="my.package (uninstall)"
directory="profiles/uninstall"
description="Uninstalls the my.package add-on."
provides="Products.GenericSetup.interfaces.EXTENSION
Products.CMFPlone.interfaces.INonInstallable"
post_handler=".setuphandlers.uninstall"
/>