Well no, if you read the part about Secure Aggregation, Google has no way of knowing which piece of training results comes from which device, they can only see

Well no, if you read the part about Secure Aggregation, Google has no way of knowing which piece of training results comes from which device, they can only see the aggregated results of a batch. So sure, technically the training results based on your data are still sent to Google, but that's not really the concern they're addressing. They're addressing Google having a record in a database of every shop you visited in the last week and such and that data getting in the wrong hands (or being used wrong by them). What if they could benefit from training on that sort of data, without ever actually storing it themselves?