probably just like google's federated learning of cohorts thing. they still cluster you, but instead of collecting your browsing activity from partner websites

probably just like google's federated learning of cohorts thing. they still cluster you, but instead of collecting your browsing activity from partner websites, they do it locally using browser history that doesn't leave your device, and the net effect is that you have an equivalent of a browser cookie or additional http request header that doesn't identify you, but does identify your cluster memberships. some people are still not ok with this, i'm on the fence.