I'd add following information (in a new paragraph) to part 126.96.36.199. Behavioral Changes of Migration Guide:
In RHEL 5 DHCP option "next-server" was used to specify NFS server containing kickstart file when ks option was used alone without any value. This was changed to option "server-name" in RHEL 6.
Point of reference in Installation Guide:
option ks of part "32.10. Starting a Kickstart Installation" which is updated with original of this bug (bug 653655)
*** Bug 730758 has been marked as a duplicate of this bug. ***