It's very annoying if I do want to see that channel, just not THAT video. You also have to be careful with that button because there's no way to selectively unblock channels. There's a feature to undo your entire Do Not Recommend / Not Interested history but not to undo it for an individual channel / video.

You should know that do not recommend channel has never really worked. Especially if there are any videos from that channel in your history.... ever.