When using swap --grow in a kickstart file
without setting --maxsize parameter at the same time, anaconda imposes a restriction on the maximum size of the swap partition. It does not allow it to grow to fill the device. The maximum size is given by the formula provided in section 4.18.4 of the RHEL5 Installation Guide - "Recommended Partitioning Scheme". The swap guidelines provided in the kickstart documentation are incorrect.
For systems with less than 2GB of physical memory, the imposed limit is twice the amount of physical memory. For systems with more than 2GB, the imposed limit is the size of physical memory plus 2GB.