VS Code has a lot in common with webbrowsers. VS Code is (as e.g. the older Atom) mostly implemented using web technologies HTML, CSS and JavaScript that execute in a runtime forked from a browser (Chromium).

I assume the grand parent is, at least partially, referring to this essay [1]. Here, the browser and HTML/CSS/JS is complimented for its dynamic nature and low barrier to entry, similarly to Emacs. In that sense, VS Code, like Jupyter, is a perfect example of the webbrowser gaining functionality of Emacs.

[1] https://steve-yegge.blogspot.com/2008/04/xemacs-is-dead-long... (the section: "The bad news: the competition isn't the IDEs")

I'm 99% sure that's not what he means. He's talking about the power of emacs.