My best guess is that Google has some kind of reciprocal data-sharing partnership with one of the entities that was aggregating data on this guy for whatever re

My best guess is that Google has some kind of reciprocal data-sharing partnership with one of the entities that was aggregating data on this guy for whatever reason, and somehow all or part of whatever file they have on him is exposed via Chrome. It's definitely possible that Google actually doesn't have that info on you. Not a lot of companies spend the amount of money necessary to pull data from the primary brokers/aggregators, and when they do, they likely don't do it for all of their customers.