The conventional mechanism of oscillatory phenomena in the NO + H-2 reaction on noble metals is supplemented with the temporal reaction route, providing fast removal of atomic nitrogen from saturated N-ad layer via NHad species as a catalyst. The total sum of lost valences at a given adsorption site is taken as a degree of local surface imperfection. A semi-empirical evaluation of this approach regards an enormous advantage of N-ad atoms at a grain boundary against perfect terraces in the activity of NHad formation as a driving force of both spatiotemporal and rate oscillations. Besides, NHad species are expected to obey an "easy-come-easy-go" principle enabling their ready formation as well as high diffusivity and reactivity. Mathematical modelling at fixed realistic step constants reveals three kinetic region-attractors related to a steady state, regular oscillations, and total reaction suppression by adsorbed oxygen atoms. .