I'm an introvert too...but I agree with him a tiny bit.
I don't think a shy child is being manipulative. I certainly think they should be able to warm up to pp at their own pace (it takes me a while too). And making small talk is a huge effort for me.
BUT it helped me a lot as a teenager and even now to realize that my fear of what people think of me holds me back from being able to help others. In fact, when I don't say anything to someone b/c I feel shy, they often interpret that as me being snobbish or disliking them. Just like an extrovert who dominates the conversation could be considered self-centered, me not talking at all in some situations is also self-centered.
I do think that quote puts a really negative spin on the issue though especially when talking about young children.