You are vastly overestimating how much that information is worth to Google. Their average revenue per user is a pittance compared to the $5 per user per month you’re paying as a GSuite customer. They’re strongly incentivised to make sure your data isn’t misused in any way. It’s not worth jeopardising hundreds of millions in future revenue to show slightly more relevant ads to a handful of folks.

The strongest endorsement I’ve seen for GSuite is that even direct competitors to Google have no issues using it. They trust Google with their data that much.