I also don't think they addressed how borrowing against the wealth doesn't require any immediate taxes (and is often low interest, given how being a billionare means you get more favorable terms). There's nothing stopping someone in that position from just deferring taxes on the money they currently have, borrowing against it, and then investing that to turn into more money with taxes deferred even further so that they can use the proceeds to pay the previous deferred taxes and keep the difference.

That requires their investments to keep going up in value. That doesn't last forever, the assets that people borrow against eventually need to be sold to pay back that loan. When they sell to make payments, those are taxable events.