Fictitious sale = deemed disposition. Same thing. If you can't pay the tax from cash you have lying around you will have to actually sell some of the investments.
Now I do get that selling a business might not be as easy as selling (part of) a liquid stock. But take the real estate example again. Selling your real estate empire seems much harder than selling some of your NVDA shares to pay the tax. If you aren't prepared to sell your business though and you want to hold onto it, why would the government be inclined to believe that you really want to leave and never come back so to speak?