Another forum's data that I've seen lines up with what dataguy shared. Some pages significantly up, others significantly down. I agree, this looks more like a document level multiplier and not a site-wide to me.
And that makes sense with the softer information we have. Remember this new algo factor was more than a year in development. That sounds like something quite fine-tuned, and also not something that uses only broad brush factors like backlink quality or bounce rates.
A couple of people have floated the idea that reading level might be in the mix - something we know Google measures. It couldn't be the whole thing.
I also noticed that Google people have gone to some length not to use the phrase "content farm" which might indicate a domain level multiplier. Rather they talk about quality and usefulness.