> I challenge you to explain what they measured
I read the study, maybe not extremely carefully. Here is my imperfect recollection: the goal was to see group effects, not just individual people. They chose 100s of villages in different parts of the country, divided them in pairs of similar ones, then applied public measures in one set and kept the rest as controls. Most of measures were giving out masks of different types publicly, combined with public messages, and various incentives. Then, they measured number of people who turned up visibly sick, and send observers to measure mask compliance and level of SD. I summarized the results here previously.