Model I, presented in Fig. , is particularly salient in the context of recent computational work that investigates molecular hydrogen atom transfer reaction landscapes when coupling a molecule strongly to a cavity. In Ref. 61, Pavošević et. al. model the proton-transfer reaction of a malonaldehyde molecule in the strong coupling regime. They found that when using self-consistent QED electronic structure methods (such as QED Hartree-Fock and QED Coupled Cluster level of theory), one observes a decrease in the barrier height of the proton-transfer reaction with electronic strong coupling. Our model through the PFS theory (Eq. 17 provides an intuitive explanation for this effect.