My understanding from talking is that internally they set a high bar for telemetry data, which includes non correlatable data through techniques like data slici

My understanding from talking is that internally they set a high bar for telemetry data, which includes non correlatable data through techniques like data slicing and differential privacy. In the case of private relay, I believe they are using privacy pass such that a token indicating authorization is anonymous on use. So say, Apple knows who someone is, but Cloudflare and the like who do the actual producing can only tell that Apple authorized proxy access and (for HTTPS) what domains are being accessed. So Cloudflare in this example may be able to get some statistics of use and share them with Apple, but it will be more about the relative popularities of pornhub.com and cnn.com, and not what percentage or who frequent both.