Not surprising considering they have a records of taxing a lot from their citizens[1]. Well, I guess if that means better public facility then everyone is okay with that.
Stock markets will always get advantage over cryptocurrency in eyes of authorities. But yes taxing cryptocurrency is still a mystery. Governments need some chunky mechanism to do so.
I don't really know how personal taxing works there but I bet most of the time they will depends on individual conscience to actually report their income. Or, just straight up collect data from every centralized exchange on their territory and then links every user with real identity.
[1]
https://tradingeconomics.com/south-korea/personal-income-tax-rate