To the extent that is a real issue, it's not even approximately just for billionaires; again, the point of this bill isn't to deal with structural problems rewarding the rich at the expense of the working class, its to raise a little money making a symbolic gesture at a handful of people while preserving the features benefitting the wealthy at the expense of the working class. The action does not match the problem is that it supposedly addresses.

If you wanted to fix that problem in the system I describe upthread (and you’d do basically the same in the status quo system, leaving the broader problems the system upthread fixes in place), you’d tax non-cash assets as income at market value less purchase price at the death against the estate after subtracting any unused advance-recognized income (and likewise adding in any leftover deferred income.) Nothing is then “unrealized forever” for tax purposes. Not for billionaires. Not for hundred-millionaires. Not for anyone.