The phrase 'rev-up, throttle back' is just an easy way to remember the order you should increase/reduce power with a constant speed prop.
I.e. when increasing power 'rev up' meaning increase the pitch (revs) first before increasing the throttle (mp) and when reducing power reduce the throttle (throttle back) before reducing revs.
The phrase 'overboosting' generally is referring running a power setting that has the throttle too high and prop lever too low but realistically if you look at the cruise power settings tables from the engine manufacturers you will see 'oversquare' (i.e. >25MP/2500RPM) settings like 24 inches MP/2100 rpm etc as perfectly acceptable for a particular pressure altitude.
From what I have learned researching the matter/talking to engineers etc it is actually best for the engine to run the highest MP/lowest RPM combination approved by the manufacturer for the particular in flight conditions. This is more or less because you are running the actual engine components at a lower speed (albeit with increased torque demands due to the increased pitch).
Hope this has cleared it up.