All that this part in the introduction is really saying is that identification is important to IoT. Much as we can say that, for electronic banking transactions, privacy is important (because otherwise people could read your financial transactions) but authentication is more important (because otherwise people could actually steal your money, which is worse), this introduction claims that identification is the most important security objective for many areas, including IoT. It's not saying other objectives are not important, and whether or not you can objectively rank these criteria and agree that identification comes out on top isn't really the point - it's just saying that identification is an important objective for IoT.
As for why it's important, suppose you have an IoT device that unlocks the door to your car, or to your house. Before unlocking the door in response to a request, it's really important that the system is able to determine that the request came from your unlocking device, and not from someone else's unlocking device - i.e. it's important that it identifies your device. It may be that you couldn't care less about privacy - if "unlock my door" were the only message that's capable of being understood by the system, for example, then even if you encrypt it any eavesdropper will still know what the message is, so you gain nothing by concealing it.