I don't have an invite and can't check, but whenever the UI changes, it looks like the only possible effect is swapping the <body> tag out for a new one.

Obviously if JS is disabled, this will just navigate to a new URL and load an entirely new page.

But if JS is enabled and the new <body> tag does not contain any <script> tags, then the only thing going over the wire is HTML after the page loads the first time.