The equation for stiffness is in post #3 and is not open to subjective debate or people's opinion. IF (and big if) the given tension stays constant and the racquet head slightly contracts, which I see when taking off the racquet (albeit almost negligibly) and for a given elastic string like NG contracting ever so slightly in length, the relative deflection can decrease, thereby the Stiffness can mathematically increase without adding energy to the system, Period.
While I agree the OP may have overly sensitive OCD fingers and tendencies and it may be in his/her head, it doesnt change the fact that no laws of physics were violated.
As for the 5 minute claim, no comment.