Why RHEL6.4 updated from RHEL6.0 doesn't have `yum-plugin-security` installed by default?

Issue

• Installed Red Hat Enterprise Linux 6.0 with kickstart file containing following %packages section,

  %packages
  @base
  

  • Then updated it using yum update command and it became Red Hat Enterprise Linux 6.4.
  • In the same, the package yum-plugin-security is missing.

• If the machine is installed with Red Hat Enterprise Linux 6.4 iso with the same kickstart file containing following %packages section, it installs yum-plugin-security.

  %packages
  @base
  

• Is this expected behavior or a bug?