We explore a statistical-theoretic origin of the linear surprisal theory with respect to final energy disposals to a given vibrational (rotational or translational) mode in chemical reaction dynamics under a fixed total energy, As a consequence of a variational statistical theory, exponential distributions inherent in the linear surprisal theory, along with the necessity of the so-called prior distribution, arise quite naturally from a standard statistical rate expression without information theoretic reasoning or the maximum entropy principle (MEP).