Steering linkage - Downward play in track rod ends

My '89 460 300GD is due for MOT soon. All trackrod ends display about 3mm of downward travel in the ball joint when pressure is applied from above. There is no upward slack or lateral travel.

This can be demonstrated by allowing a bar to rest on the track rod, and then levering or pushing down slightly (while the vehicle has all wheels on the ground) - the end of the joint compresses down 2 or 3 mm on the gaiter, but immediately returns to its rest state when downward pressure on the bar is released. There is no corresponding upward play regardless of whether the wheels are on or off the ground.

Is there a spring mechanism between the ball and the cup, causing this observed behaviour, or is this genuine play that could lead to a fail on MOT?