unable to match on machine name of permission

If the "system name" of a permission refers to the machine name, the filter is not matching on the machine name value.

For example, I have a node type "aircraft_event" that is referred to as "Aircraft Activity" in the permission title and description. Searching for "aircraft_event" produces no matches, while both "aircraft act" and "aircraft_act" return the correct matches.

Am I misunderstanding the search being done?