Can you explain how this works? I have my wealth in stocks, I use those stocks as collateral for a loan. To pay back this loan, I have to either get money from somewhere, or hand over the collateral to the bank. Let's say "get money from somewhere" is taxed (to avoid circular reasoning), so that leaves trade loan collateral for loan cash, which is on net no different than selling the stocks.
This is not taxed? And wouldn't it be infinitely easier to close that loophole, than taxing the estimated profit for the next N years, which is what unrealized gains tax amounts to?
Take out another (slightly larger) loan against the stock. As long as the stock grows faster than the interest rate, you should be able to chain loans together forever. You need to only borrow a portion of the value of the collateral to provide a buffer from volatility, but that should also mean the loan is very safe and thus at a low interest rate.
To close the loophole you would need to be able to tax borrowed money which creates its own set of dangers.
The very first sentence of TFA gives it away: Recently, my story as a Norwegian entrepreneur facing an unrealized gains wealth tax bill many times higher than my net income went viral
Many who are in the position to control how their compensation is doled out (board members, C-level) will often take it exclusively (or nearly so) in stock, specifically so they never have to pay taxes on it. Famously, several have taken $1/year incomes - e.g., Mark Zuckerberg and Steve Jobs, while Elon Musk didn't even bother with the charade and took $0/year.
* Side bonus: in the US, corporations paying out performance-based compensation like stock get additional tax breaks, so it's not just the executives which win the taxation game while doing this.