The yoke cable's length is part of the leverage geometry and along with arm length determines the final leverage. The goal is usually to balance maximum leverage against lever and brake shoe travel considerations.
A manufacturer will tune yoke cable length to accommodate different caliper arms, or by design to reduce leverage in either brake to better balance braking forces when levers are squeezed equally. Lastly, on some frames, the yoke length has to be set to accommodate physical factors, ie. going around a tube when necessary, or because the hanger is too close to the brake.
My advice is to assume the maker knows what they're doing and use what's spec'd if it fits, until/unless you have the expertise to change to better suit your personal preferences.
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