Since the JCW uses a different clutch from the Cooper S (presumably to handle the added hp), it appears that MINI feels the stock Cooper S clutch is not up to the task.

Upgraded clutches are generally intended for MINIs that have performance upgrades - they are designed with higher clamping forces to handle the additional horsepower / torque

MINI Countryman Clutch Problems Reported problems with the factory original clutch used on the early MINI Countryman are easy to find. While more problems seem to related to the All4 version of the Countryman they are by no means isolated to them. The experiences are varied. Some MINIs only suffer ...

The clutch operates using brake fluid. It draws off the brake fluid reservoir via a black tube on the side. Fluid flows from the reservoir into the cylinder above the clutch pedal (when there is a negative pressure). Then when the pedal is pushed the pedal cylinder pushes fluid through the tube into the clutch slave cylinder which activates the clutch.