Be rational and consider all options:

1. The data is accurate and captures all coronavirus cases.

2. The data is not accurate and does not capture all coronavirus cases.

I read the entirety of this thread as though HN assumes only 1 is possible. If 1 is correct, then HN’s inferences sound reasonable (habitual mask use, practiced social distancing).

But what if 2 is correct? Is there any disincentive for governments to accurately test and capture all cases? Is there any particularly outsized disincentive for Japan to do so?

I leave the above questions as an exercise for the reader.