Let’s compare the relevant paragraph in the Biden-Suga and the Biden-Moon statements: The shorter one with Korea does not mention China, Hong Kong, Xinjiang, UNCLOS, and (predictably) the East China Sea. But it does mention Taiwan, South China Sea, and international law.

U.S.-ROK Leaders’ Joint Statement https://www.whitehouse.gov/briefing-room/statements-releases/2021/05/21/u-s-rok-leaders-joint-statement/ The United States and the Republic of Korea oppose all activities that undermine, destabilize, or threaten the rules-based international order and commit to maintaining an inclusive, free, and open Indo-Pacific. We pledge to maintain peace and stability, lawful unimpeded commerce, and respect for international law, including freedom of navigation and overflight in the South China Sea and beyond. President Biden and President Moon emphasize the importance of preserving peace and stability in the Taiwan Strait. As democracies that value pluralism and individual liberty, we share our intent to promote human rights and rule of law issues, both at home and abroad.

U.S.- Japan Joint Leaders’ Statement: “U.S. – JAPAN GLOBAL PARTNERSHIP FOR A NEW ERA” https://www.whitehouse.gov/briefing-room/statements-releases/2021/04/16/u-s-japan-joint-leaders-statement-u-s-japan-global-partnership-for-a-new-era/

President Biden and Prime Minister Suga exchanged views on the impact of China’s actions on peace and prosperity in the Indo-Pacific region and the world, and shared their concerns over Chinese activities that are inconsistent with the international rules-based order, including the use of economic and other forms of coercion. We will continue to work with each other based on universal values and common principles. We also recognize the importance of deterrence to maintain peace and stability in the region. We oppose any unilateral attempts to change the status quo in the East China Sea. We reiterated our objections to China’s unlawful maritime claims and activities in the South China Sea and reaffirmed our strong shared interest in a free and open South China Sea governed by international law, in which freedom of navigation and overflight are guaranteed, consistent with the UN Convention on the Law of the Sea. We underscore the importance of peace and stability across the Taiwan Strait and encourage the peaceful resolution of cross-Strait issues. We share serious concerns regarding the human rights situations in Hong Kong and the Xinjiang Uyghur Autonomous Region. The United States and Japan recognized the importance of candid conversations with China, reiterated their intention to share concerns directly, and acknowledged the need to work with China on areas of common interest.