RPM Changes
Its probably too far back in your memory but revisit Effects of Controls (UK PPL syllabus Ex 4) which covers effects of disc loading and airspeed on RPM. With the governor turned off, forward cyclic will initially reduce disc load and RPM will transiently drop, then the increase in airspeed will lead to an increase in RPM. With the governor on, it will sense this RPM increase and reduce throttle to maintain 104% RRPM. This is evident by the reduction in RPM.
CH