There is no content listing in an appendix, while there is in a regular chapter. It would be nice to have a switch for publican.cfg that would enable the chapter-level TOC in an appendix.
It is unlikely we will do this. There are too many XSLT options in docbook to provide an option for everyone on a per book basis. This kind of decision should be made at the brand level, where it is a simple change to include tocs at many levels.
Assuming this was done in a brand, let me know directly if you need any assistance getting brands working.