GP's critique is not that web browsers render SVG and PDF in addition to HTML. It's the outsized role of JavaScript specifically: our browsers execute arbitrary (possibly user-hostile) code while simultaneously trying to protect us from its effects.
The point I was trying—perhaps failing—to make, is that it doesn't make much sense to create a web browser that can render "web documents" but not "web apps", since the concept of a "web document" is basically "anything you can access over HTTP", and so a "web browser" — a tool for viewing arbitrary "web documents" — really doesn't work as a concept except by adding some mechanism to execute arbitrary code in the service of viewing those arbitrary documents.
That mechanism doesn't necessarily need to involve code being delivered directly from the same server the document is coming from, mind you. It could instead involve an out-of-band app store, where accessing a URL zero-installs a heavily-sandboxed plugin required to view it, and loads it into the browser. (Implementations of this: iOS App Clips; Sandstorm grains.) But those apps are usually still created by the same developer as the document anyway, so there's little difference between this out-of-band zero-install app approach, and having Turing-complete web documents. Either way, the developer of Boogle Maps can still mine bitcoin in the background while you have the map loaded.
The B2B productivity/collaboration app space — where you can expect that all your users are mainly using full PCs — is firmly all-in on in-browser web-apps, with their mobile experiences being second-class afterthoughts.
I imagine apps are better at being apps than a web browser, and due to their complexity webapps are also tightly coupled to a specific brand and version of browser, so you have less compatibility problems by bundling your preferred vm with your application.
I'd argue today that "apps" do pretty well whether they're in a browser or native. Native Slack is pretty good. Web Google Docs/Sheets is pretty good. VSCode is almost the same regardless of where you run it. But equally, Sketch and Ableton Live are also pretty good. Native Teams and Zoom are travesties of usability and stability.
Basically, I don't see consistent patterns of good or bad between web and native apps to justify your comment that "apps are better at being apps than a web browser".
Most GUI apps, native or otherwise, get associated with a brand. Especially the good ones. I'd buy Ableton swag, I love the brand that much.
The VAST bulk of web apps are NOT browser version specific. It's largely only bespoke, internal corporate apps that are tied to one version of a browser.
