Why are reverse lookup shown as authoritative?

[blrmaani]

I have a cache-only server [ DNSHOST2 in the picture below ]

DNSHOST1  ( authoritative DNS server for zone myzone1.com )
     |
     |
DNSHOST2  ( cache only DNS server )
     |
     |
CLIENTHOST

I used nslookup on CLIENTHOST to lookup names and ip-addresses in debug
mode.

The replies for names shows as non-authoritative whereas replies for IP
address
shows as authoritative. I was under the impression that all cached
replies are always
non-authoritative. 

Please clarify.

thanks
regards
Blr