I opened a ticket with support.

‌I've only tested it on iOS 9, yes. And it's not a problem with the iframe not loading when offline, that's a given. It's a problem that the entire article won't load and simply exclude the iframe content. And yes, it's all iframes. In DPS 2014 when things like this would happen with an overlay we'd usually have some text that would state, this feature requires an Internet connection. But I can't get anything in the article to load, it's just a white screen.