If their citizens continue to hide money in the form of crypto, all exchanges in South Korea may be required to do KYC and report to the authorities.
There are always the good people and the bad peoplin the sociaty. Sometimes the governments have to make such hard statements in order to threat the people so that some of those bad actors may pay the taxes (this even includes the taxes to be paid on fiat money). However in most cases , government won't just seize assets for all those who do not pay taxes, they simply do not have the infrastructure and resoruces to have this massive plan implemented.