as I already mentioned in the title, net ads dns [register/unregister/gethostbyname] doesn't support IPv6 addresses.
It's weird to have IPv4/6 DNS records but not having reliable way to manage both of them.
I see that here on the Bugzilla is already reported gethostbyname not supporting IPv6: https://bugzilla.samba.org/show_bug.cgi?id=13473 , but I didn't want to write there instead I've created new report.
*** Bug 13473 has been marked as a duplicate of this bug. ***
This bug was referenced in samba master:
*** Bug 10197 has been marked as a duplicate of this bug. ***