The report's scope is limited because it focuses on the trading activities of Upbit, Bithumb, Coinone, Korbit, and Gopax. However, there was a report that the number of
South Koreans crypto investors holding large sums in overseas crypto CEX accounts increased over the years. They prefer foreign exchanges because of the South Korean restrictive trading environment and the inability of local exchanges to compete with others like Binance.
Other factors might have contributed to the drop in crypto transactions and not necessarily a shift of investors to stocks.
You can not account for every single crypto investor in a single country. Even if you ask for KYC from every single exchange, there will be people who are doing it on P2P or with privacy coins. However, you can get a certain feeling with the sample size, and this is not like just 10 people we are talking about here.
However, what I disagree with is the location, it is not just Korea. I do not think that other nations did research on this, but if you did, you would see that everyone around the world gets out of crypto when it is a bear market, and they end up buying up stocks; it's not only Koreans.