"and then every-so-often batches those metrics out to Apple's servers" means they do know, even if we trust the implementation. For example, if you publish an

"and then every-so-often batches those metrics out to Apple's servers" means they do know, even if we trust the implementation. For example, if you publish an ad that only matches the word "fnord", and the metrics reveal that you were shown that ad at least once, Apple can work out that "fnord" appeared in your chat.