The "or-status-disavowed" filter is one which for it to have any effect, has to be used together with one or more other filters from the backlinks table.
Therefore, backlinks that will be filtered into view when "or-status-disavowed" is used together with another filter, is the collection of all disavowed backlinks and those backlinks not disavowed, meeting the criteria of that other filter.
An instance when this is useful is when one wishes to see the list of all backlinks that are not passing link juice. That is disavowed links and all links with statuses such as NF, 404, 302 etc.
Therefore, instead of creating the separate lists that meet the above criteria, "or-status-disavowed" allows you to do this in one list.