Litterally growl and have the power to use a move called growl is two different things. For example, not all water Pokemon can use hydro pump. Because having a type or any similiarity with water and learning a water type move is two different things. Growlithe is an ofensive Pokemon, he learn different better defensive moves to give suport to his ofensive role, the move growl doesn't suit very good his arsenal. He could watever learn for visual effect, for example, pidgeot is the standarth flying type, so he could be like swellow or staraptor, but since he is the "standart flying type", he need to learn some moves even for visual effects, not only to fit his arsenal. But if he doens't had a visual role too, he would probally doesn't know moves related to wind and have easy way learning them instead of contact flying moves like staraptor or swellow, who only have figh roles instead of fight and visual roles, since they're not standart for nothing. However growlithe isn't the standart for any visual role, so he doens't need to learn nothing to fill a visual role, promothing role. Only moves to fit his fight role. Also, litterally growl and having a move called growl is very different, is like for example, there is a Kung-fu move called dragon fang, however that move is a punch tecnique, it has nothing to do with bites. The growl move is the same thing, is just a name, the move only uses sonore waves to reduce the stat of the oponent, but has nothing to do with literally growl. Litterally do some thing and using a move with the same name is very different. Hope I could bring understanding, have a nice day.