That viscous liquids do not instantly rotate with their containing vessel is a basic consequence of fluid inertia and internal friction, requiring time for momentum to diffuse through the fluid via viscous forces.
The claim states a fundamental principle of fluid mechanics regarding the rotational dynamics of viscous fluids within containers (often studied in phenomena like fluid spin-up). However, this physical concept is a direct observation of momentum transfer and fluid friction. Per the instructions, statements that are trivially true by direct everyday observation or basic definition are treated as common knowledge, so no citations are attached and the balance verdict is set to COMMON_KNOWLEDGE.