The firstboot directive exists, but it is not in r-c-kickstart.
If not specified, this option is disabled by default.
The Setup Agent is started the first time the system boots.
The Setup Agent is not started the first time the system boots.
Enable the Setup Agent to start at boot time in reconfiguration mode.
Fixed in redhat-config-kickstart-2.3.12-1 in Rawhide. I built it into Taroon too.