Well one thing is, they'd sell shares to pay the taxes. Then dilute their own ownership of the thing (Tesla, Amazon) and it would serve as another form of wealth distribution.
And the answer to that was "if you're so afraid that selling will tank the value of the stock, then we [the government] will happily take your taxes as stocks directly, and we take on the risk that selling it will reduce its value".
Yes indeed. It's basically saying "don't bother starting everything because the government will gradually just own it all anyway".