My point was that in an airline environment you can't have hundreds of pilots all doing what they think is best. In my outfit, we set standard when cleared to climb to a Flight Level and QNH when cleared to descend to an altitude. A cross check is compulsory when a change is made. The standby altimeter remains on QNH until passing FL180 going up and has destination QNH set prior to TOD. It can therefore be used for "passing altitude" reports if required.
If a stop climb/descent clearance is subsequently issued it is up to the crew to make sure the subscale is properly set.
Plenty of other ways of doing it, but this works well for us.