Indeed, it really does seem that Google told Danny that there was a technology barrier that prevented the application of those signals (OR, application of the signals the way they most wanted to do it).
But, with Hummingbird, that barrier has evidently been removed. In my view, this is the amazing hidden part of Hummingbird that has not gotten the visibility it deserves.
My next Search Engine Land article will discuss this even more.
I also loved Danny's reminder that the original launch of the +1 button was positioned by Google as a way to help Google find the best content on the web.