Back when I thought it was two mattresses, I thought it couldn’t be at the top because the right mattress probably wouldn’t be held up like that. But since it’s one mattress, it can relatively easily be held at that angle with most of its weight resting on the step.

And that’s my main reason: it really seems like the mattress is being pushed towards that step, and I believe it’s being pushed by gravity. Doesn’t make as much sense for it to be pushed in that direction by someone.

I’m not married to it though, it’s a really tricky picture.