Omitting out-of-control additional records from responses?

Right now when searching for records to include in the additional
records section of a response, tinydns includes any records that it
knows about.  But can anyone suggest a realistic scenarios where this
is useful, rather than only including records within the "control"
(i.e., nearest parent name with SOA/NS records)?

E.g., right now if you query "dnsq a shinobi.dempsky.org
ns1.everydns.net", ns1.everydns.net includes glue records for
ns[1-4].everydns.net.  Theoretically DNS caches could recognize that
ns1.everydns.net is authoritative for everydns.net, but in practice I
don't know of any that do.  As such, it seems like a waste of
bandwidth and CPU cycles to include these records.  (On the other
hand, checking this is potentially a waste of CPU cycles for zones
that only use in-bailiwick names.)

The (proof-of-concept) patch below omits out-of-control records from
the additional records section in authoritative responses.  I think
the test for flagauthoritative could be removed without harm, but I
can imagine legitimate use cases where non-authoritative responses
include out-of-control records that are still within the bailiwick of
the client.  (E.g., if example.com were to delegate sub.example.com to
sub-ns.example.com.)

Any thoughts?

--- tdlookup.c.orig	2009-09-21 17:28:19.000000000 -0700
+++ tdlookup.c	2009-09-21 17:47:22.000000000 -0700
@@ -249,6 +249,8 @@
       }
       else
         if (!dns_packet_getname(response,arpos,bpos + 2,&d1)) return 0;
+      if (flagauthoritative && !dns_domain_suffix(d1,control))
+        continue;
       case_lowerb(d1,dns_domain_length(d1));
       if (want(d1,DNS_T_A)) {
 	cdb_findstart(&c);