Of course, he is not saying that, he is just explaining how whatsapp is actually storing the messages.
No, he's saying that in order for the messages to be available, they have to be stored locally and since most people need access to the messages from their phones, it makes sense to do it this way to ensure that all messages are stored on the phone, instead of users ending up with some messages on their phones and some on their PCs.
So are you saying that a desktop PC's hard drive can't handle storage of some text messages but a phone can?