Board Thread:Episode Discussion/@comment-410526-20160206155158/@comment-410526-20160208210326

I'm sure he would have been able to defend against that, and probably had Aura remaining, so even if she did land a hit on him he wouldn't have been taken out. Not to mention he's fought with her for years and knows exactly what she's capable of, so I don't think Blake would be able to catch him off guard using her Semblance like that. He's probably seen that way too many times to be blind to it.

And besides that, I think he knew what Blake was doing, he just didn't care. He wants to make Blake suffer, killing her with a clean beheading doesn't really achieve that. He let her escape so that he could continue to torment her. Notice he doesn't even give chase when he could easily outrun an injured Blake who is also carrying Yang's unconscious body.