authoritative rDNS

[Jim Pazarena]

I set up a subnet on my server, complete with rdns, and ARIN has been 
adjusted for my two dns servers (ns.qcislands.net & ns2.qcislands.net)

the subnet: 23.235.75.0/24

if you do a lookup of, for instance: 23.235.75.10
and bounce that nslookup off of other dns servers, SOME say:
Authoritative answers can be found from: <ns & ns2>

others, well, at least google 8.8.8.8 do not show anything as
authoritative, altho the IP DOES resolve.

I am curious if 8.8.8.8 isn't trying, or instead, am I missing
something which 8.8.8.8 considers incomplete and therefore 
un-authoritative ?

I just want to make sure my setup is accurate. Thanks.