That's the way the testing and measuring is approached ..
The typical pilot training thing about strange balls in teacups is useful if explained appropriately but, near invariably, it is a case of the blind leading the blind and the explanations tend to be more fanciful than useful.
Stick force for positive static stability can be thought of in terms of "if I relax the load, the aircraft initially would seek to return to the trim speed".
In terms of balls and cups .. the analogy is "if I let the ball go .. its initial movement would be in the direction of the bottom of the cup".
Either way static stability is to do with the aeroplane's being at a fixed off trim attitude and looking at what it might want to do if you were to let go of the stick/ease off the stick load .. dynamic stability looks at what it actually does.