I found this, I'm wanting to get a pixel tablet in about a week or so. Title just got me wondering a bit, though it's probably just a little bit sensationalized
I think it'd be nice if they offered an option without the base for $400 especially since the hub experience on it as it is currently isn't very good. All hub mode does currently is turn it into a glorified digital picture frame with the home controls button in the bottom corner and the Google Home experience isn't as good as a Nest Hub.
As it is right now, I wouldn't consider the Pixel Tablet as a replacement for the Nest Hub.