https://bugs.openldap.org/show_bug.cgi?id=10299
--- Comment #3 from Greg ratness@gmail.com --- This is just a note explaining my thinking, don't take it as advocacy.
In man 8 slapacl, -u and -b 'point at each other', and -u saying "a fake entry with the DN given with the -b option is used" had me to where my interpretation was that -u is scope-limited just to the DN specified in -b. That you then indicated the -rest- of the ACLs aren't looked up, that surprised me.