I'm speaking about the pictures on the website OP links to. They even say "As you can see in the example below, the upsampled image looks blurry – one would hes

I'm speaking about the pictures on the website OP links to. They even say "As you can see in the example below, the upsampled image looks blurry – one would hesitate to call it enhanced." It's blurry, because they use an algorithm that produces blurry images. Lanczos, for example, would produce a much sharper picture at the expense of some minor artefacts. They don't show A+ results anywhere in the blog-post at all.