Ice shedding (on-the ground) could be addressing ice on blades or ice on stator vanes.
Blade ice is shed via centrifugal load while stator vane ice is shed by areodynamic or windage loads.
The idea is to shed the ice before it buils up to a mass that could cause trouble when shed (damage and/or engine surge)
Ice formed at low power conditions (low temp in the fan area) would take too long to respond to increases in temperature, hence the need for power-ups of N1 to get enough centrifugal load or aerodynamic loading.
Typically The certifying agency would take a dim view having to use these procedures normally on any icing formed in-flight