You are correct that land intervention is different. Land masses are the only places that man can establish long term claims and successfully defend those claims. But despite the advent of air travel and control, we, meaning those with sea lanes access, are still essentially naval powers. It is not those who can 'control' the oceans, but rather those who can impose his/their will(s) upon them, who will continue to dominate global issues and create that 'bandwagoning' effect around those issues.
There are many forms of stability. My take is that China is least interested in the form of stability that came from moral consensus. My house borders three neighbors and we, without putting anything on papers, agreed that it is immoral to trespass on each other's property without permission or good cause, such as a fire, for example. When China claimed to be owner, not merely master, of the entire South China Sea region, that is a clear sign of China's desire to dominate Asia and impose a Chinese version of stability irreverence of neighbors. That body of water is meant to divide Asia into discrete pockets of manageable issues.
I have the book The Japan That Can Say No by Shintaro Ishihara. Nationalism was rife throughout that book. In a way, I do not consider that any discredit to any Japanese. But what made possible Japan's economic, and hinted at military, rise was that Japan was protected by the US Navy. Protected in the sense that Japan's livelihood was near total dependency on the oceans and the US denied others, including the mighty Soviets, the ability to deny anyone access to the same. Simply put, the US denied the possibility, never mind probability, of anyone to gain control of any body of water on the oceans. That made possible for Ishihara's misguided belief that Japan could say 'No' to the US. Never mind the inevitable backlash from the few US Congressional blowhards, which fizzled out to nothing anyway.
With the claim to be owner of the SCS, China is not merely saying 'No' to the US, but 'F U' to the US and to China's neighbors. China is trying to do what the US denied others during the Cold War: Control a body of water on the oceans.
This is not merely denial of control like how the US have done, but actually claiming the SCS under territorial sovereignty. You can have a vast desert as part of your country and as long as your neighbors respect that claim, it is irrelevant if that desert is barely inhabited. If anyone tries to trespass on your property, you would raise the army to defend that piece of barely habitable land. That is the privilege and burden of territorial sovereignty. China believes she has that privilege to the SCS and is equally confident that she can defend the SCS.
If Asia is foolish enough to accept China's claim to the SCS in the name of regional stability, then the Asian countries might as well submit to China as vassal states. May be China will give you a lollipop in the form of something similar to the French Union.