Hi Bryon. The techinfo document type is primarily intended for use in Service Information Manager where the topics are authored in XML and the structure is defined in SIM Publication Structures. The map exists as a way to publish the entire content of the Publication Structure but we didn't expect it to be human-authored.
Since there is no way to specify an Appendix in SIM, we did not add it to the TIA map. Also, the stylesheet does not have support for it.
If you need an Appendix then you would specialize the map and add your own support for it in the stylesheet.
