Yeah from what I understand Jenkins would only really be used to run tests against the code. So it doesn't package or compile anything since as you said there's no reason to. It creates a directory structure that contains the output from things like phpunit and what not.
I think that ultimately you could write a plugin (if it doesn't exist) to create rpm's with the code. I'm now realizing how nice war files are, haha.http://jenkins-php.org/