that's not how push works. usually, google would only know you received a notification, but not it's contents. that "dummy" notification wakes the app up, which decrypts and shows the real notification.
content aware stuff runs entirely locally on your phone, so no data is sent to google (unless you have telemetry enabled, in which case the reply or action you used will be sent to google together with the next telemetry data upload)
yes, some apps actually push the content directly through the push system, but that's not how this is handled in most apps that handle private data in notifications.