[econner]

You still owe capital gains on the original proceeds, deferred a few years and with a possible 10-15% basis step up. This isn't zero capital gains tax.

If you happen to have a billion dollar exit on your reinvested capital gains that can be tax free, but you're still paying tax on the original gain.

[modeless]

It might as well be zero when the original "investment" is a token amount you put in at the founding of a startup.