Does anyone else wonder why the author doesn't go all the way but stops at HTML and DOM? How does "div", "h1" help here to "convey meaning" or attach "behavior"

Does anyone else wonder why the author doesn't go all the way but stops at HTML and DOM? How does "div", "h1" help here to "convey meaning" or attach "behavior", or serve any other purpose usually associated with HTML that may make sense for responsive/accessible documents but not apps? AFAICS the DOM is a crappy scene graph for apps, made barely tolerable through lots and lots of CSS ad absurdum, thereby complicating if not outright sabotaging text reading for generations to come. SVG would be a much more rational choice (with parts where typography and text flow/flow layout actually play a role still in an essential HTML subset). Or even pure JS-based immediate mode rendering, possibly with offloading of new layout model computations into JS libs portable across JS-enabled browsers, like the Houdini API is proposing? The proposed syntax merely seems like it's opportunistically driven by what's present in the JS language but isn't really pushing the limit despite the tone.