snapshot backup doesn't seem to include all tables

I have “Include all blog database tables in this archive. This will automatically include new tables.” checked in my snapshot settings. As I watch it process through the list of tables, it’s very clear that not everything is there… seems like it’s skipping all of the sub-sites in the database. Am I missing a setting of some kind? Or does the archive process skip sub-sites even if the plugin is network-enabled? Confused…