Prius towing a travel trailer? Yes.

Thanks for the new pic of the Prius/trailer combo. It explains a lot that was not obvious in the OP's pic. Yes, I agree with the OP that the trailer IS sitting on a non WD hitch on the Prius, however, both pics posted explain a lot as what it's all about. The pic IS an optical illusion and likely staged as a person viewing only see's one side at a time.

The setup is an advertisement for Prius as is clearly evident on the non as OEM built Prius. Both pics show the narrow Prius parallel to the lines on the pavement while the 2-3 foot wider trailer is canted on an angle. Not normal to be towing like that! There's a reason for it to be this way! If it were pulled in as normal for fuel etc the trailer wheels would be over the yellow line on the pavement on both pics. Why? The Prius rear wheel width is 60 inches and the trailer wheel width is 80" to 90" or 10" to 15" per side wider.

Very evident in the OP's pic as the Prius is nearly an exact side view while the trailer front is at a 29 degree angle and should be at a 6 degree max angle which I didn't account for in my CAD overlay rendering because I failed to recognize the angular illusion created by the staged parking. That was my fault.

The trailer in the pic is about a 15' to 16' long box with approx 3 for the hitch making it about 18' plus total length. I looked up the 50's thru the 70's single axle trailers and they are all over 3000 lb weight in weight which requires a very min of 300 lbs hitch weight at 10%. Even a totally stripped out with no propane in the tank shown is still well over 2000 lbs.

I am posting the Prius specs below and the link.

Add approx 200 lbs for the driver with no passengers and no other cargo. the hitch weight, 12 gal of gas, and over 200+ or 300 lbs of weight on the ball and you are at or over the Prius GVWR. So, I went down to our Walmart and there was a bright blue Prius in the lot the same 4 door model as the OP's pic and I parked behind it. Got out with a tape measure and measured the rear bumper height from the ground and then put just my 210 lbs on the bumper and measured it again. Hmmm, 3-1/8" drop! The Prius in the pics doesn't drop a bit! Sure is not an OEM setup and what else isn't OEM on the staged advertisement Prius?

Survivors of Titanic said ship broke in half while sinking.
Engineers said not possible.
Glad this didn't take as long to resolve.

And yes, I respect engineers, but sometimes........