Read the mot Test section not the main policy section, this cover is included only in the finest cover. And according to what it says Discs are included under the following conditions.
Providing the vehicle has at least three months MOT Test remaining at the start of this cover and the MOT falls due within the period of cover, this MOT Test Insurance covers the cost or repair and/or replacement and/or adjustment to the specified parts listed below as a direct consequence of such parts being cited in a notification of refusal to issue an MOT
MOT Test Insurance Cover TableComponent
What is Covered?
Braking system ABS modulator, sensors and computers, brake calipers, discs/drums, load compensator, master cylinder, pipes, hoses and cables, wheel cylinders
What is not Covered?
All other components