The reissue certificate functionality was introduced as a hack in 1.9 as the grades were stored in the certificate_issues table, so if the grade did change for a user, the old grade was still displayed on the certificate. This setting was introduced so that a new issue would be created if the setting was turned on.
This is no longer. There will only ever be one issue per user and certificate in this table. The grade, studentname and date are not stored in the issues table, but generated when the certificate is viewed.