I worked for Data company for a year. We absolutely used Census and ACS as baselines and checks. In fact, there was some talk about getting rid of ACS in Congress and we got emails about "EMAIL YOUR CONGRESSIONAL PERSON, DEMAND ACS STAY. Here are talking points."

I am indeed sworn to not reveal lots of data I knocked on doors for. My memory isn't that good, especially compared to the database it went into, anyway.

I hope it's not a baseline for individual records, but my assumption was that the census data would be pretty useful as a baseline for aggregate information, especially when it comes to comparing to private sets they're working with.