Andy is well known for undersizing tow vehicles and advocating such set ups (like a 33' airstream behind a Dodge Charger sedan). Not my idea of safe but....
His opinions in the linked article are pretty standard for him.
While his odd ball combos might be fine for 70% of towing, it's the other 30% of the time that can cause disaster. I'll give an example. The GCWR of a Charger sedan is much lower than what's needed to tow a large airstream RV. Now put that combo up a steep mountain grade in 100* temps. That's where it's going to show up as a mismatch. The frontal area of the car is small, which reduces it's cooling ability, and transmission cooling system and clutch material durability, and so on. The right tool for the job is important when you face extreme conditions.