The article says this

Sen. Wyden’s proposed Billionaires Income Tax (BIT) would tax the wealth gains of billionaires and those with consistent income above $100 million. Currently, such investment gains are only taxed if the underlying asset is sold. But the ultrawealthy don’t have to sell to benefit. They can secure low-interest loans secured against their rising fortunes and live luxuriously tax-free. Under Wyden’s plan, such wealth-growth income would be taxed every year just like worker wages are now. The Joint Committee on Taxation estimated this proposal would raise $557 billion in new revenue over the next decade from just a small number of ultra-wealthy oligarchs.

I don’t like wealth tax for a number of reasons, but a capital gains tax on unrealized gains that phases in after a certain amount seems very fair. The phasing in is important because average people’s homes and other assets should be untouched imo, but after a certain amount of unrealized income it should be.

I’d also suggest taxing secured low interest loans as a form of realized capital gains.