reports -> Availability report -> by trigger template report does not work in nested configuration, only for directly linked templates.
for example, templates like application_servers, email_servers etc all might be linked against template_linux, and only then to hosts. in such a case, availability report does not work - only hosts that are directly linked against template_linux are shown in the report.
this is very limiting, as it prevents either template nesting, or usage of availability reports. trigger configuration section properly shows the upstream template, and this report should be aware of that as well.