You're absolutely right, and I would hope people have at least some awareness of this. (There's enough trailer accidents & wrecks to indicate against that, sadly.)

That said, looking at the numbers still makes some sense to get a rough understanding of the design space of these cars though. (And, well, the numbers I was replying to were confusing the heck out of me.)

(My source: German class BE driver's license = car with heavy trailers. You're limited to 0.75t trailer OR (car + trailer) ≤ 3.5t without that, in B. The E is a separate exam, both theoretical and practical. Aside from theory bits on how cars with trailers behave, you have to parallel park or T-turn a trailer to pass it.)