I recently noticed that boolean fields (Deceased, Do Not Email, Do Not SMS, etc) are all displayed as "Yes" on contact and membership reports, regardless of their actual values. The data itself is correct and is fine elsewhere, such as in search results and contact displays. The issue seems to be only on report display. The report filters work correctly on those fields, only the display is wrong. I checked my production system, my dev system, and the public demo system at wpmaster.demo.civicrm.org and I see the same thing.
My system is CiviCRM 5.2.2, WordPress 4.9.6, PHP 7.1.16, MySQL 5.7.21.