If you leave the throttle and accept the RPM decay, then it is all crystal clear and makes fine sense.
But if you are supposed to increase throttle to regain 2,400 RPM, and that results in the same RPM but slower airspeed, then something is apparently more complicated (prop efficiency varying with airspeed is all I can think of as a reason for how that would work out...).
With a wobbly prop I think it is all much simpler; then you could have the same MP and RPM but lower fuel flow at best economy (or LOP), thus giving you less power, less airspeed, and the governor setting finer prop pitch to maintain RPM despite less power.