Not only that, but the egg on the box is actual size too. It just looks smaller in that picture because most of it is covered in cardboard. Here's the same box in good lighting.
Unlikely. The simplest explanation is generally most plausible, either:
OP got an already opened box from someone, failed to notice the box was already open, failed to read the text in the box, failed to notice the prominent chocolate bunny on the box, failed to understand the purpose of the cardboard in the box, accidentally obscured text on the box with poor lighting, unintentionally took a misleading picture, and posted it into the internet as a genuine complaint.
Or, OP saw protective cardboard around a fragile hollow chocolate egg and decided to lie on the internet.
The box was clearly designed for a larger egg. The fact they made the image the same size doesn't neglect the fact that shrinkflation has occurred.
The only reason the box size hasn't changed is to fool buyers on the potential size of the egg. If it was box was correctly sized, most people would have selected a different egg.
Yes but I don't think that is the complaint from OP. It seems more about the size of the box suggests the contents will be less cardboard and more chocolate.
IMO they could have made it a couple of inches shorter but at least it's cardboard and not plastic 🤷♂️