We consider an interconnection between the oscillator (spin-boson) model of the continuum outer-sphere electron transfer (ET) reaction and its stochastic dynamical description in terms of generalized Langevin equation (GLE) for longitudinal polarization The oscillator Hamiltonian derived from the GLE can be reduced to its conventional spin-boson form in the limit of the infinite frequency of the primary polarization mode, called solvaton coordinate. In the framework of the Golden Rule approximation the ET rate expressions of both (solvaton and spin-boson) theories are exactly the same. This is shown without invoking a condition of the infinite solvaton frequency. A hypothesis concerned with a physical nature of bath oscillators is suggested. These modes, embodying dielectric friction effects within the GLE description, are associated with transverse polarization waves of a continuum medium.