Why don't audit_log plugin in percona 5.6 support include/exclude databases

Hi All
I want to use audit_log plugin in percona 5.6,but I found that audit_log plugin in percona 5.6 don’t support include/exclude databases, thus audit_log plugin in percona 5.7 provide this feature.
If I can do this work for percona 5.6 in kernel just change the code in audit_log plugin? if not ,why?
thanks all.