Essentially yes. There's also some tweaking the CSS pointer-events property on those canvases to allow mouse events to fall through when you're not hovered over

Essentially yes. There's also some tweaking the CSS pointer-events property on those canvases to allow mouse events to fall through when you're not hovered over 3D content. I envision most people will want to position their 3D objects relative to some 2D element like a div.