It seems pretty clear that Anthropic models have been specifically trained to be good at generating three.js (JavaScript 3-D Graphics) code, so given current state of AI code generation in general, I don't find three.js models/animations as indicative of anything other than the model's ability to write three.js code. When Fable was first released the day-1 demos of it on Twitter (presumably from people who were given…
Anthropic models are excellent at working with Blender APIs, other industry standard 3D modelling programs and tasks, and game libraries that have nothing to do with Three.js.
Three.js is a quite popular library; and browser-based apps are more easily sharable and more portable. So models having a preference for using it when unprompted doesn't suggest anything, just like how models using React or Tailwind by default doesn't suggest anything.