I think there is an overlay that enables inheriting attribute-values, I am sure I read it somewhere, a few years ago, but I cannot find it, not with Googling.
The intended behaviour is the following:
For this record:
dn: cn=David,ou=Sales Department,o=Example Co. objectClass: organizationalPerson cn: David sn: Jones
Normally, if you do (ou=Sales Department), you don't find David's record. But with a certain overlay enabled, you can. It is as if the attribute in the DN is inexplicitly there assigned to the record.
Forgive me if I was wrong.
Best.