Knowledge base table is not captured in the update set whereas the user criteria tables are captured in the update set.Summarytables extending sys_meta_data table are captured in update set. knowledge base table contains data rather then configurations so it is not extending sys_meta_data table since it is a data table. m2m user criteria tables (kb_uc_cannot_contribute_mtom etc) contains criteria configurations so it have meta data rather then a transactional data so that is the reason we are extending sys_meta_data table.