You might be arguing against a straw man. I don't think PG was saying "Current, actual proposals will significantly dent inequality".

I think he was saying "People misunderstand the issue. They're concerned by inequality, but think that reducing inequality amounts to the same thing, and inequality is per se bad."

Reading this in combination with other essays, pg is likely worried that a seemingly innocuous change could have an outsize impact on startup formation, precisely because they're so marginal.