I think you are right they are targeting large advertisers with significant spend.

It's a unique approach in that they don't need a lot of granular attribution data, but instead use higher level aggregate data. As a result it's easier to integrate with all kinds of media campaigns.

You need to be able to provide impressions over time for your early funnel ads and conversions over time for your late funnel touchpoints. They use some econometric time series techniques to analyze and estimate the impact so you can focus on whats working.