I'm sure he's wrong. For comparison a Hanomag 1,3 Liter from a similar angle. The unknown car has another radiator grille, other wings, wiper fixed above the windscreen. It also appears larger and wider to me. I wouldn't be surprised if it was a four-door sedan.
My guess (without any proof) would be a prototype for a Hanomag Sturm successor in the style of the 1,3 Liter.