Could you provide any more info on how this test works? Where are the tests performed from, or do they run client side? Does it query name servers directly, or if not, how does it avoid ISP-level DNS caching influencing the results?
Tests are from your connection using whatever resolver chain your ISP has in place. It uses a wildcard name record and an 8 byte json-p include. It alternates between downloading that file from the same origin using a cached DNS record (test run up includes 3 downloads to prime the resolvers with a cached hostname) and an uncached record (a new randomly generated hostname) and reports the difference in time between the two.