Being able to drag it is only part of the equation. You still have to stop and control it. In my past I had a Jeep CJ5 with heavy duty gearing and a big engine with lots of torque. My boat was big and heavy, and the jeep had no problem pulling it. That combination was pretty hairy controlling it on turns and if the trailer would start to sway. I had a panic stop on the interstate, and the rig jack knifed in a hurry. After that, I used a lot heavier truck to tow the boat trailer.
I think the trailer is used to transport car dollies and things like that. If you look at the picture, the sides of the trailer consist of channels for the wheels of the dollies.
While this may be physically possible, I very much doubt it to be a safe practice if the trailer is loaded, or under less than optimum road conditions. The towing vehicle should be at least close to the weight of the towed unit, and the short wheelbase of the TDI would allow it to be pushed off track very quickly if the trailer developed any variation from a straight ahead motion, in direct line with the wheelbase of the car.
I'm thinking the highway patrol may have something to say to the driver, if they se this.
It has the wide mirrors so he has been at it for some time. Trailer brakes? Wonder what weight plate is on the car? You can put a farm plate on a car, seen it lots. Jetta automatic trannys are not known for their durability.