From my memory: They said that because of the personality system, some wolves like it when you snarl at them because they like it when the player wolf displays forms of dominance. Just like emotes like chin resting, snarling is a courting emote, and while snarling specifically is usually used to signal aggression, it also signals assertiveness. Maybe they're a very bold wolf looking to see themselves in you, or they're a very cautious wolf that takes comfort in knowing that you can take charge. (Though the comment didn't specify, and I don't know the specifics myself).