If you are at cruise flight power and you get carb ice, selecting carb heat without adding power will still get more then enough heat into the engine to melt the ice.
I am sure you are right but carb icing isnt just going to occur in just one spot in the sky especially if you are level. There are two stages to managing the threat.
1 Is to remove the ice
2
Is to stop it forming again
Selecting full power makes it less likely to form again. Someone mentioned a problem if you are leaned-well carb heat enriches the mixture so that will not be a problem and in fact continuing with step two is in fact to lean the mixture if you need to run with carb air hot to stop further icing.
I note our C152 manual says also carb air hot & select full power as indeed does the CAA safety sense leaflet, or it certainly encourages the use of full power.