[thaumasiotes]

You missed my point. Do WhatsApp, Instagram, or Facebook Messenger have working ephemeral messages? Or do they have marketing that claims they have ephemeral messages?

The feature is fundamentally impossible in exactly the same way as DRM, because it is DRM. You're sending someone a bunch of data and saying "now, you promise not to look at this, right? Except once."

[neksus]

As someone who works on Instagram Direct, I can assure you we have ephemeral messaging.

[thaumasiotes]

How do you stop people from recording their messages?

Snapchat takes two approaches (that I know of): First, they don't stop it, but the messager is supposed to be notified when it happens. They know this doesn't work and can't work, though; avoiding screenshot detection isn't even considered a reportable bug. (see https://hackerone.com/snapchat )

Second, they have a legal barrier, in that using a third-party client to communicate over Snapchat violates their terms of service.

Notably, neither of those makes the messages any more ephemeral. This makes sense, because stopping people from recording messages that you send them is not an achievable goal. Barring some sort of supernatural influence, it's no more achievable for Instagram than it is for Snapchat.