In this paper, it is shown that the experimental values of the nonextensive scattering entropies $S_L (p)$ and $S_theta (q)$ for the pion-nucleus ($pi^0 He, pi^0 C, pi^0 O, pi^0 Ca$) scatterings, in the energy region corresponding to $Delta (1236)$ resonance in the elementary pion-nucleon interaction, are well described by the entropic optimal resonance predictions $S_L^o1 (p)$ and $S_theta^o1 (q)$ and when the nonextensivities indices are correlated by a Riesz-Thorin-like relation: 1/2p+1/2q=1.