any arbitrary binary population, including massive binaries.

The $\gamma$ formalism can indeed lead to orbital expansion, as well as an increase in the total energy, for mass ratios close to $1$. However, if interpreted as a dynamical-timescale process, this increase must prove just as unphysical as a negative efficiency in the $\alpha_\mathrm{CE} \lambda$ formalism. In the following section we will also demonstrate that a single-valued $\gamma$ is not robust against small perturbations in orbital parameters, and is thus unable to explain both evolutionary stages in all instances. Therefore, when attempting to describe both phases of DWD formation simultaneously, the $\gamma$ formalism is subject to similar fundamental physical problems as those found using the $\alpha_\mathrm{CE} \lambda$ prescription. Rather, in $\S$ \[1stMassLoss\] we demonstrate that stable but non-conservative mass transfer can account for the expansion in the initial phase, bypassing the need for any parametrization of this stage.

In order to understand what the $\gamma$ mechanism implies, and to contrast it with the $\alpha_\mathrm{CE} \lambda$ formalism in a double-CE scenario, let us analyze the energy and angular-momentum balance during a first and second CE of a binary system that is a potential progenitor of a DWD system. After the first CE, this 