Originally Posted by
Tu.114
The aim of this procedure is to remove any ice that may have gathered on the fan before increasing power for takeoff. Of course, the blades are not heated, so the only way to remove the ice is to put its brittleness to use. By increasing and decreasing power, the blades will bend and twist a little and the ice will hopefully pop off and take its leave down the bypass duct.
So the easiest answer to the question is that the individual engine manufacturers have determined during their tests that their prescribed procedure will work best to achieve said aim.
What may play a role in there is the different blade lenghts resulting in different centrifugal forces at a given rpm, different materials, airfoils and so on that may well result in different bending characteristics in individual blades - if so, PW with its shorter duration seems to rely more on shedding the ice by twisting the blades and CFM rather relies on centrifugal force.
So if You want something beyond speculation, why not contact the engine manufacturer or Your technical pilot?
Very insightful thank you !