I haven’t read the article, but usually when people like this don’t have any stocks, it’s to avoid a conflict of interest, but they do potentially own something like a whole market etf that’s being managed by a 3rd party. Something like XGRO
That varies though. Some really do have nothing.
Edit: And while it seems like in this case it’s true to the intent, technically, owning an ETF share isn’t owning a stock. You don’t own the underlying stocks with ETFs