I think it doesn't support 'vt' because the techniques are adequately demonstrated just with faces and normals, so it would be more code without serving any ped

I think it doesn't support 'vt' because the techniques are adequately demonstrated just with faces and normals, so it would be more code without serving any pedagogical purpose. The author would, I think, not suggest you copy this code and try to use it as a library or something, but that you should develop the skillset to be able to write code like this when you need it.