what is, or is not referred to as a "unicorn" is not a core mechanism of wealth creation.
all they said was "I wish ... call companies unicorns when they “profit” a billion dollars a year."
obviously the valuation mechanism can't change, but we could all agree to be less impressed by noisy valuations, and more impressed by realized profits.
Thus the company is not actually worth Y valuation and pretending otherwise ignores the terms of the deal.
EX: If the company is nominally worth 1 billion at the time of investment, and later sold for 900 million the last investor may actually have profited via money that early investors never received.
You are correct, however, selling 0.00001% of my company to some schmuck for 100$ does not mean people are willing to give me 1 billion dollars for te rest of it. Many so called "unicorns" seem to be closer to that scenario than to actually having a market valuation of 1 billion dollars.
You're asking for the core mechanism of wealth creation in technology to be dispelled.
If enough people, over a credible amount of time, say that a company is increasing in value, and if they back each such assertion with a small percentage of that stated value, then eventually said company can be taken to the public who hopefully will agree and put up their money to validate the game.