Another quote from the article: "The data that is required to 'turn on any push notification service' is quite invasive and can unexpectedly reveal/track your location/store your movement with a third-party marketing company or one of the app stores, which is merely a court order or subpoena away from potentially exposing those personal details."
"App developers can encrypt these messages when they're stored (in transit they're protected by TLS) but the associated metadata – the app receiving the notification, the time stamp, and network details – is not encrypted."
Another quote from the article: "The data that is required to 'turn on any push notification service' is quite invasive and can unexpectedly reveal/track your location/store your movement with a third-party marketing company or one of the app stores, which is merely a court order or subpoena away from potentially exposing those personal details."