The focused purpose, I think, gives it more of a "purpose built tool" feel over "a chatbot that might be better at some tasks than others" generic entity. There's no fake persona to interact with, just an algorithm with data in and out.
The latter portion is less a technical and more an emotional nuance, to be sure, but it's closer to how I prefer to interact with computers, so I guess it kinda works on me... If that were the limit of how they added AI to the browser.