There is no right of wrong answer here, as in many brewing techniques. Higher mash temps produce more dextrinous wort and CaraFoam is a dextrine malt so the answer you were given is at least partially correct. However, IMO it is simpler to add a small quantity of CaraFoam to a recipe to add some dextrines. Boosting the mash temp can also effect the fermentablity and attenuation of the beer. A thick, malty beer like a Scotch ale might be great with a high mash temp. But if I want to brew a Helles, for instance, with a dry finish but a touch of extra mouthfeel the mash can still be done at 148/150F to create the overall profile and finish of the beer and a small percentage of dextrine can be added for the extra touch of mouthfeel.