A tanker is equipped with baffles, yet it can still roll over due to liquid movement inside the tank. What explains this?

49 CFR 383.119(c) (differences in handling of baffled/compartmented tank interiors versus non-baffled vehicles); AAMVA CDL Manual Section 8.2.4, p.8-8-2

A tanker with baffles can still roll over, which surprises many new drivers who assume baffles solve the surge problem entirely. Side-to-side surge is left uncontrolled by standard baffle design and can combine with cornering or sudden steering forces to tip a high-center-of-gravity vehicle. This gap is exactly why tank endorsement training treats baffled and unbaffled tanks as sharing overlapping, not identical, risks.