That's not the same thing, it's a whole different thing to do a "rpm --rebuild *.src.rpm" and to actually take a upstream source package it with a spec, patch it to make it compatible with other things in the distro and test them in different setup.

The challenge anyway is not to rebuild packages or make packages it is to actually maintain the build farms and the build tools.

source: i work for Red Hat (not doing any packages work tho) and I used to work for Mandrakesoft on Linux-Mandrake when we were basically rebuild Red Hat rpms to our flavour.