This is because the clutch fingers are on a pivot. As you push the fingers in towards the front of the engine, the contact surface of the pressure plate moves back, towards the rear of the car. So, if the clutch disc is wearing, the contact surface of the pressure plate moves towards the front of the engine, with the clutch fingers moving back towards the rear of the car. So if your throwout bearing position is fixed, this decreases the clearance between the fingers and the throwout bearing.