The insert exhibits a very thin profile with a circular area that would be for a USB-C to Lightning cable and a square area that could be for paperwork and the traditional stickers that come with Apple products, as it looks too thin to house EarPods. A thin depression around the entire insert is likely where the iPhone itself would sit.
Apple typically makes nearly its entire product packaging out of recycled paper products, with the iPhone box inserts firmly glued into the outer retail boxes. The rendering of this insert looks more like plastic, which would be unusual in a modern Apple retail box, but it could simply be due to the rendering process not accurately representing the molded paper products.
We’re a little skeptical of the veracity of this for now, but if true, it would be a strong piece of evidence that Apple is indeed planning to not include EarPods or a power adapter with the iPhone 12 and demonstrates how much thinner the overall iPhone box could be without those items included.