Torque is defined as a rotational force applied about a point, and internal torques generated by reaction wheels change a spacecraft's angular momentum without exerting net external force, meaning they inherently act about the spacecraft's center of mass as a fundamental principle of rigid-body dynamics.
The claim describes a fundamental physical principle of rigid-body mechanics: internal torque devices such as reaction wheels exert pure torques that change the angular momentum of a spacecraft about its center of mass. This is a basic mechanical truism that does not require empirical citation from specialized literature, so it is classified as common knowledge.