[zxxon]

>> The majority of game engines scene graphs are retained mode 3D abstractions.

... but they are not built on an abstract retained mode API. That would be the wrong level of abstraction for a Web API that people can build on properly. I think that's the point here.

Unfortunately, Web APIs tend to be far too high level while missing out on low-level hooks, like the disaster that is Web Audio (and media playback in general).