This is by spec according to the ietf:
http://tools.ietf.org/html/draft-li-dnsext-ipv4-ipv6-02#section-1.2
per the spec during the "transition time" between v4 and v6 AAAA records should be queried first followed by A records if there is no answer. From the above doc:
"Due to large-scale applicable for IPv4, it will take a long time to fully transit from IPv4 to IPv6. During the transition period, IPv4 network and IPv6 network will coexist.In most cases, the host will not know whether the address of the other side is IPv4 or IPv6. According to current practices, the host will send an AAAA query first. If there no IPv6 address has been retrieved, then an A query will be issued."
Unfortunately dns clients are not smart enought to know if IPv6 is turned on or off - so the above will always be followed.
Regards,
C. Paxson