[bloqs]

that it stores all of your messages on a server, and not on your phone. Your phone being in plane mode disconnects it from the internet, but you are still able to browse your messages.

[ffpip]

You don't need to 'prove' it. Thats their selling point. Access your messages on every platform.

[fedorhk]

Isn't it as they describe it? Unless you created e2e chats specifically (Secret Chats).