named manual says about -4:
       -4
           Use IPv4 only even if the host machine is capable of IPv6.


I used named -4 but log output said:

22-Sep-2014 14:20:18.922 using default UDP/IPv6 port range: [1024, 
65535]
22-Sep-2014 14:20:18.923 no IPv6 interfaces found
...
22-Sep-2014 14:20:24.899 no IPv6 interfaces found

It said that 81 times within 16 minutes.

On another named -4 run, I had it configured with:
  listen-on-v6 { none; };
and it had the same behaviour.
I didn't configure all the various other transfer etc tunables for v6 
to try to turn it off.

So why is use-v6-udp-ports done if -4 switch sets disable6 to true? 

And why is isc_net_probeipv6() done if disable6 is true?

Either let's use disable6 or let's fix documentation.

Thanks