Interesting. With a little hackery, it should be fairly easy to get this working with PlayCanvas. I'm not sure why it needs to use a new element type though (canvas3D).
Canvas does not support all the 3D elements needed for spatial recognition and accessibility via 3D audio. I'm hoping to read through and see canvas3d support that feature.
What does Canvas have to do with audio? Web Audio has the necessary components to do spatialized audio. And spatial recognition is an input. Canvas is for output.