This deal shows the reality of the Pacific Islands. Ever since World War 2, when the Japanese and the US fought for the dominance over the pacific, and US won, the entire Pacific is de facto US colony. The pacific islands have independence and sovereignty in name only. They were allowed have a facade of independence when US power was uncontested. But now that China has risen up and is more powerful than the Soviets in the Pacific domain, US is under pressure. US will not longer allow these so called countries the same leeway it did before.
US and Australia are ofcourse part of the same Anglo-Saxon empire, so naturally Australia is given some part of the US domain as part of its colony.
Not just Tuvalu, the more power China gets and more desperate US gets, you will see US and even Austrlia toppling governments with coups, doing these kinds of deals and setting up bases all over the pacific.
For China to have presence in the Pacific, it will have to physically either fight for it. Or do its own influence and coup operations to set up its own friendly governments. But most likely any kind of coup not backed by huge Chinese naval presence will not succeed and US will takeover again. So, the only way China can have any meaningful influence in the pacific islands is to have a huge navy with 15+ aircraft carriers that is able to comfortably overpower US navy in the pacific. Only then China will have any chance of setting up bases and real influence in the pacific islands.