An outside individual purchasing shares is not the same as employees accessing liquidity.

As one example, SpaceX is privately held but routinely does funding rounds with large investors so employees can sell shares and access liquidity[1][2]. A $10,000 minimum purchase amount is trivial for those investors.

[1] https://www.reuters.com/markets/us/elon-musks-spacex-raises-...

[2] https://www.reuters.com/business/aerospace-defense/spacex-fu...