Dick / reversethrottle
You roll on throttle BEFORE lowering collective because...lowering the lever naturally closes the throttle via the corrollator, ie: the lever and throttle are connected.
Simultaneously lowering and rolling raises the possibility that your amount of throttle rolling will be at least partially cancelled out by your amount of lever lowering, ie: the former will trail the latter.
Thus, to be sure, it is better to at least get the engine power recovery process started by first rolling on throttle that little bit BEFORE. Of course, getting the lever down is also very important, hence the 's' word tends to get used. We are talking milliseconds, here.
Bring back the old days, eh Dick?