To expand, I believe the idea here is that what libertarianism is in principal matters less than what it collapses to in practice, similar to the difference in communism.
And there's a central tension that libertarianism, as far as I'm aware of, doesn't resolve in how to promote individual freedom across a highly economically unequal society.
Trusting those with all the capital to act in anything other than their own best interest doesn't seem a solid foundation.
In a true libertarian society, since it's small government, the government wouldn't help rich people stay rich. You could just declare yourself owner of Tesla, and nobody would stop you except the former owner of Tesla, if he can afford to stop you. Nobody believes in true libertarianism.
If communism is whatever the USSR did, and feudalism is whatever medieval England did, I see no problem asserting that libertarianism is whatever the USA does.