He goes on to say 'Supposing you had such a browser, what would you do with it? The overwhelming majority of websites would not render correctly on it.' - A very good point, but equally applicable to a Gemini browser.

IMO, they have confused the network protocol with the presentation. You don't need to drop HTTP in order to change the way websites look. Likewise, you don't have to implement HTTP features that you don't like (e.g. cookies). This just strikes me as another mistaken belief that rewriting code from scratch will solve all your problems.