Why does Red Hat Enterprise Linux 5.3 prompt for a timezone when one is specified in the kickstart?

Issue

In Red Hat Enterprise Linux 5.0 through 5.2, kickstart did not  enforce setting a valid timezone.  If an invalid timezone, e.g., GMT,  was specified in the kickstart file, the kickstart would proceed anyway  (and possibly incorrectly set the clock since the zone was not  valid!).  Note: The correct zone name for GMT in kickstart is Etc/GMT