Maybe they are going for the Netherlands route
Wealth tax in The Netherlands
The way it’s calculated is that the Dutch government assumes a 4% growth / yield from the assets exceeding €30k. This includes cash, investments, bank accounts, cryptocurrencies… Everything!
So, for example, if you have €100k on your bank account, you can keep the first €30k tax free. The government will assume that you made 4% return on the other €70k, amounting to 2800€. And you’ll need to pay 30% of this assumed profits in taxes, which is 840€.
Once again, this is enforced regardless of whether you made 4% ROI, whether you kept the money in checking account, whether you realized any gains, or whether you doubled your money and didn’t realized it.
Again, it’s not this straight forward and it’s a progressive system, but for simplicity, it’s effectively around 1% of the total amount of wealth you owned on 1st of January that fiscal year.
So, it’s not a substitute for capital gains. It’s also not tax on unrealized gains. It’s capital gains regardless of gains.