That's an interesting point. That's sound at least plausible that mobile notifications could be monitored by intelligence.

Still, the point would be the same: they are likely inventing a story around the airport wifi, and someone/something is watching messages directly on the provider side.

Very likely, I remember this from last month https://www.wired.com/story/apple-google-push-notification-s...

Snapchat notifications don't have the actual message content, the notification would have been '$Name sent you a chat'.