It is certainly a WebGL Context.

Running this on one of the examples.

let c=document.querySelector("#canvas");

c.getContext("2d"); >>>> null

c.getContext("webgl"); >>>> WebGLRenderingContext { vertexAttribDivisor: vertexAttribDivisor(), drawArraysInstanced: drawArraysInstanced(), drawElementsInstanced: drawElementsInstanced(), createVertexArray: createVertexArray(), deleteVertexArray: deleteVertexArray(), bindVertexArray: bindVertexArray(), isVertexArray: isVertexArray(), drawBuffers: drawBuffers(), Yu: null, canvas: canvas#canvas }

c.getContext("webgl2"); >>>> null

Of course that doesn't stop it from using any amount of software rendering layers before it hits the canvas, but it's a good sign.