@adamatari By sleep together you just mean 'slept in the same bed' right? I dont recall these 2 being intimate - have they even kissed beyond jokey or friendship type kisses?
That's the joke.jpg
Honestly, even if they've never passed first base, they're further along than almost anyone else. Their ambiguous relationship is kinda the point for the series, but who says they aren't serious? The way I see it, their special treatment here is highlighting that - they're always holding hands, telling each other "I love you", and basically acting like a couple. It's only because we're looking from the outside and seeing them as a special exception to normal rules that we don't see that they've been a couple for a while when everyone else is still figuring it out.
Even in-universe they're seen as something like a special exception - it was mentioned that first year students consider meeting them a lucky charm somewhere? But everyone takes for granted they are together without thinking much about what that means.
Normally I wouldn't say this over one picture, but the contrast is too striking in context. The picture hit me right in the heart. I can't imagine that isn't on purpose.