What is the practical risk the CDL manual describes if a driver loads a tank completely full with a dense, heavy liquid?

AAMVA CDL Manual Section 8.2.7, p.8-8-2 ("A full tank of dense liquid (such as some acids) may exceed legal weight limits.")

An overweight tanker isn't just a paperwork problem; it's an enforceable violation that can result in fines and being placed out of service. Knowing that dense liquids reach their weight limit before the tank is visually full helps a driver avoid overloading.