Hi,
It's the inversion of the tactic that the british army had used when they disguise the tanks like lorries - british want to hide that they have a lot of tanks ready to battle, the germans want that they think that they have a lot of tanks ready.
As said in the caption it's a wood and canvas superstructure done on the field, so I think that artistic license here works fine and if it looks like the photo, the dimensions are not important, probably they will be something diferent between them.
If it helps I can give you the dimensions of the Panzer Ib that it's said to me the vehicle that they intend to represent.