IMHO, it's worse than that. Most sites only added a AAAA record for their website, and frequently didn't for their DNS server. So they weren't *really* doing a complete IPv6 test, IMHO.
There is a reason for that. First of all, we (my employer) took this as a brief test to simply see how much IPv6 traffic there really was, and who and what would actually attempt to reach us by IPv6. The idea here being to attempt to identify IPv6 native networks. We had to do this in a way that did not break our existing IPv4 services. We run some services that we do not consider "breakable" and our user profile is much different than a web site is. We might have millions of clients on a network that are, for the most part, identically configured. So for example, if one users device believes it has IPv6 but doesn't *really* have IPv6 (as a link local IP so it believes it has IPv6 or has IPv6 inside its network but not clean to the Internet), then there are probably tens of thousands of identically configured devices in that customer's network. So we don't face the "some small fraction of one percent are broken" problem, we face a "if one is broken, then a significant portion of and possibly all of that customer's devices are broken". If we put IPv6 DNS records in place that caused 100,000 clients to break, we would have some serious explaining to do. In this case, a very safe approach was to place an IPv6 address for our web site in DNS. None of our "business" traffic goes to our website. In the course of IPv6 day for the roughly 18 hours it was operating, we might have had 200 hits on IPv6 compared to thousands of transactions per second on our "business" protocols. The test did, however, expose a bug in a piece of vendor gear that was catastrophic to the business service. The entire piece of gear blew up that handles the business traffic in addition to the web traffic. It rebooted itself but apparently did not boot cleanly. This was bad enough but it was rather quickly placed back into service (manual kick) and happened at the slowest traffic time of the day and few/no clients would have noticed. Had we also experienced customer complaints of slow/poor/no service during the time of the test, it would have been pretty bad. So enabling IPv6 DNS had the potential to cause global problems and not limited to a single data center, it could have had global impact to the domain. Placing a single IPv6 DNS glue record and DNS server in service would have also potentially resulted in local DNS servers from around the globe that might prefer IPv6 attempting to reach that one DNS server. In other words, it would have created a potential single point of failure and possibly degraded performance. So the IPv6 DNS infrastructure is being rolled out in a planned, methodical fashion. Dropping an AAAA record for the web site was an easy thing to do that was considered very low risk (as we assumed all of our other gear could simply pass IPv6 packets without exploding) and offered some participation with the community. George (speaking for himself)