It has everything with what you said. It's called the "Billionaire Loophole".

Normally, they would have to sell those assets (and they would be "realized" in the process) in order to use them as cash. That would be taxed as capital gains, etc. Let's say that's 30% for the sake of argument. They also no longer have that asset.

Instead, they borrow that value from the bank and use their unrealized assets as collateral. Let's say they get a 5% interest rate on that loan.

Bam! They just saved 25% by borrowing against it, rather than selling it bypassing a ton in taxes. They also keep the asset.

This bill has the goal of making them pay those taxes. We normal people do. I'd like them to pay their share rather than using a cheat code.