I know nothing of childhood development, but considering the sound a cow makes is different depending on the language of the speaker, I'd assume it's less about teaching children the sound a cow makes and more about teaching the sounds that exist in your language.
Exactly. I'm not exactly an expert on the topic, but we've been visiting speech therapist with my daughter since she was 3 years. It's all about learning the sounds that you will use, and connecting the sounds to animals is just to make it fun.