While the argument makes sense, the study seems a bit suspect. For one its is basically done through taking a survey of data, and no actual measurements of the change of health resulting from drinking only Fukamushi, as opposed to those drinking only Asamushi, as opposed to those drinking none.
I mean it makes sense, as many have claimed that Matcha is one of the healthiest styles of tea because you are drinking the tea leaf with the tea. But then again just looking at this from a data mining perspective if we collected enough data on everyone in the entire world there will be significant aberrations by geographical area for certain things, some of which can be explained others which may not be able to.
But I think this is best summed up with Correlation does not imply Causality. Even if a doctors fall into this trap.