It is true except for the Extreme Editions. http://techreport.com/articles.x/15967
Faster memory does not offer any real world advantage across a multitude of applications. Even Triple Channel offers no real advantage over Dual Channel. If you check out the tests you will see that at high resolutions the i7 965 that supports over 1066 MHZ offers no advantage in Frames with faster RAM. In short for many reasons it is simply a waste of money buying 1600 MHZ RAM etc.