That is not going to happen so easily. Your car is equipped with numerous sensors so they just wont let the average increase. Throttle body is only for air passage it passes air in correct volumes to the cylinders where it is mixed with injector fired petrol so the average wont deteriorate. Cleaning throttle body helps to achieve better throttle response and better pick nothing else.
If you go for throttle body cleaning let them do it but keep an eye on idle stop screw, better mark it with some color if honda has not done so and if after throttle body cleaning if the mechanic tries to mess up with idle stop screw just kill him there and than. That screw is not supposed to be touched and once touched will require touching every now and than