Quote Originally Posted by Fyraltari View Post
But Ulfric isn't dragonborn. The Voice is just a learned skill for him, he doesn't have any dragon souls.
As I've mentioned before, an experienced user of the Thu'um can feel the presence of words of power, and as demonstrated by the Greybeards and Parthurnax sharing their understanding of several words of power with the Dragonborn without him having to consume their souls(of which, only one is a dragonsoul,) understanding of the words is a tangible force. Since it looks almost the same as a soul mid absorption, it in and of itself might be made of the same metaphysical "substance" as a dragon's soul.

In particular, the Greybeard are able to sense words of power from what would effectively be many hundreds of miles away.

Ulfric knows two shouts: Unrelenting Force, of which he knows three words, and Disarm of which he knows... At least one word, and he understands those words

Alduin may have sensed the presence of the last Dragonborn and the presence of several words of power and the understanding there off, but upon arriving at Helgen proper realized that those were two different individuals and went for a "kill everything" policy to make sure.