Yes, head-to-head does say a lot indeed. Mao and Joannie have met head-to-head nine times this Olympic quad in ISU competition.
Mao has topped Joannie 6 times out of 9 (2010 Olympics, 2007 and 2008 Worlds, 2008 4CC, 2008 GPF, 2007 Skate Canada) while Joannie has beat Mao 3 times all in the same season (2009 Worlds, 2009 4CC, 2008 TEB). If Joannie continues beating Mao, I'll be more convinced that they have a real rivalry.
Also, isn't it funny how statistics produce very different results when you adjust the size of the sample?