[vasekrozhon]

Hi, the author of the blog post here.

The section was written horribly -- while I was talking about backpropagation, I was thinking about "what can be done in polynomial time" and there's a mismatch as you explained. Thanks and shame on me, I rewrote it.

In any case, I would recommend watching the video first, the article is just accompanied stream of consciousness for those few who really liked the video.