It does this with most NPCs who have very long dialogues (like the Prophet).
I see it as sort of the player's character.
Prophet: "Drone drone drone exposition b...."
Player "Yeah, okay, I get it, thanks" :D
Haha, that's a good way to look at it, yeah. *Laughs* Though I've really only noticed it with her, mainly because she won't shut the hell up.
That said, I'm surprised they didn't add a function where the dialog won't proceed without a button press for each line (for a good example of what I'm talking about, such an option exists for Xenoblade Chronicles), and furthermore, that there isn't a mod to that effect. That would have gone a great way toward fixing the issue.