HI surveys find more gas-rich giants than the models can stock: the high-mass end of the HI mass function exceeds simulation predictions (Haynes 2011; Maddox 2015), because the feedback tuned to suppress stellar masses also overheats or expels the cold reservoirs. The models cannot keep massive galaxies gas-rich without breaking the stellar census.
In the model, every reservoir is accreted through the halo's hot atmosphere and survives only if feedback spares it, so cold gas in massive systems is doubly taxed: shock-heated on arrival and ejected by regulation. A population of giants holding huge cold reservoirs requires a gentler accounting than the framework's one feedback dial provides.
SCT stocks the reservoirs by a different route and holds them under different physics. The delivery: massive collision-seeded systems received their gas at deposition (P22, P25), reservoirs scaled by the collision mass function rather than filtered through hot-atmosphere accretion, so a gas-rich giant is a system whose deposit ran large and whose consumption ran slow, not an accounting error of feedback. This is the registered residual-gas expectation already carried by the star formation sector (recid 116): ordinary efficiency on large deposited reservoirs leaves substantial cold gas in place.
The holding: the binding is coherent mesh amplification rather than a hot particle halo (P50, P52), and the mesh term binds without the virial shock-heating bath that cooks accreted gas in the standard picture; cold gas held by a standing field in a dynamically quiet system stays cold, the same gentle-environment reading that keeps Leo T's envelope intact at the opposite end of the mass scale (recid 141). The three-way balance the models cannot strike is then unnecessary: the reservoirs were never run through the hot gauntlet that demands it. The registered population discriminant: HI-rich giants should be biased toward kinematically quiet, coherence-high environments, with reservoir mass tracking deposit indicators rather than feedback proxies. The seeding mechanics are in Paper 4, From Chaos To Collisothermal Cosmogenesis.
Keystone economy: P25 delivers the gas, P52 holds it cold. The excess is the inventory the models never stocked.
WALLABY and SKA statistics carry the kill: if the high-mass HI excess dissolves under better completeness corrections, or if the gas-rich giants prove to occupy ordinary feedback-regulated environments with reservoirs tracking accretion indicators, the delivered-reservoir reading is unnecessary. SCT separately requires the environmental bias: HI-rich giants distributed independently of kinematic coherence measures would break the gentle-holding half of the mechanism.