  Cold collisions serve as a very sensitive probe of the interaction potential.
In the recent study of Klein et al. (Nature Phys. 13, 35-38 (2017)) the
one-parameter scaling of the interaction potential was necessary to obtain
agreement between theoretical and observed patterns of the orbiting resonances
for excited metastable helium atoms colliding with hydrogen molecules. Here we
show that the effect of nonrigidity of the H$_2$ molecule on the resonant
structure, absent in the previous study, is critical to predict correct
positions of the resonances in that case. We have complemented the theoretical
description of the interaction potential and revised reaction rate coefficients
by proper inclusion of the flexibility of the molecule. The calculated reaction
rate coefficients are in remarkable agreement with the experimental data
without empirical adjustment of the interaction potential. We have shown that
even state-of-the-art calculations of the interaction energy cannot ensure
agreement with the experiment if such an important physical effect as
flexibility of the interacting molecule is neglected. Our findings about the
significance of the nonrigidity effects can be especially crucial in cold
chemistry, where the quantum nature of molecules is pronounced.
