I'm not sure I'd bank much confidence on a study that used two different surveys of kids and their parents on self-reported tea consumption and possible influenza symptoms. Also, while drinking 1-5 cups per/day was associated in their statistical significance, >5 cups did not.
If it's a tea planting area its probably more rural. Just having fewer people around is going to lower infection risks -- density is one of the reasons it's spreading fast in China.
The study doesn't mention matcha but it does mention catechins as primary ingredients responsible for health benefits. Matacha contains several times more of the substance.