There are at least two other instances for this claim, one by a Major General at China's national defense university and one by a former official at the Chinese embassy to Japan.
While these aren't official claims, they aren't being put forward by inconsequential people. At the minimum, it is a cause for concern. Chinese border disputes with India don't seem to be going well either. I vaguely recall that China recently expanded their claims to Arunachal Pradesh. I believe they also move a couple more divisions of the PLA to Tibet.
The People's Republic of China (PRC) is not a monolithic entity. Being the most populous nation on earth means that not everyone toe the official line. Hence, to refute your point:
1. Has there been any historical precedence of such claims being turned into an official claim? Not to my knowledge, but if you have any examples, I'd like to know.
2. Is there any country on earth where every single person of authority toes the official line? Again, not to my knowledge, but I don't mind being proven wrong.
Chinese claims to other territories & waters have, in some cases, evolved from unofficial to official. When eminent individuals are publicly making claims & not being slapped down, it's a bad sign. China is not the UK, where the government takes little notice of such things.
As I stated above, which of PRC's claim went from unofficial to official? I'd like to see the facts.
Sam Bateman quotes Professor Joyner as saying that none of the claims has a strong legal basis, i.e. they are all tenuous. To suggest that means that China's claim is not tenuous is perverse.
Sam Bateman said "China's claims are at least as good as other parties
", a statement I put in bold in my previous post. This is quite different from the majority of english-language media that rubbishes PRC's claim as being weaker than others (if not baseless altogether).
All the littoral states make excessive claims, but China's stands out. Unlike any other state, it claims, in effect, the entire sea, including rocks & islets close to the coasts of other countries. It also claims every rock & shoal it claims has territorial waters extending far beyond what is internationally recognised, & it breaches the principle of equidistance.
Says who? The english-language media?
Here's the facts:
Relevant bits are
However, the Chinese Ministry of Foreign Affairs has reiterated that China is not claiming sovereignty over all of the South China Sea. Although China has not completely clarified its nine-dashed line, in official diplomatic notes to the United Nations, it has claimed sovereignty over the Spratly Islands and their adjacent waters.
This is the reason many parties have called for PRC to clarify its claims in the South China Sea for decades
, which will be the basis for resolution of the disputes.
China makes arguments in support of its claims which it dismisses as contrary to international law when put forward by other countries, e.g the attachment of territorial waters & EEZs to rocks & shoals, which it condemns in rather intemperate language in other cases (e.g. Okinotorishima). It illegally sends submerged submarines through Japanese straits, within universally recognised territorial waters, & insists on its right of surface transit, while complaining about the perfectly legal surface transits of warships through waters it claims (but without any legal basis) itself. The hypocrisy it displays is breathtaking.
Submarines operating in other country's waters are new? Hasn't that been happening for the last century? Every country that operates submarines send them on "surveillance" to areas of interest, which does include other country's waters. And yet this is cause to take the PRC to task, but not other submarine operating countries?
Talk about hypocrisy.
The basis of most of its territorial claims is that territory X was part of China at some time in the past, & therefore belongs to China now. This is, of course, complete nonsense. It rejects the principle of self-determination outright.
If PRC claims territory that once belonged to it as their sovereign land, that will include the entire Vietnam (direct Chinese rule for 1,000 years, another 1,000 years as a vassal state) and Korean Peninsula (Chinese vassal for several centuries). I don't see any such claims.
Also, what the english language media tend not to hype about are the peaceful
resolution of border disputes between the PRC and several of its neighbours. For example:
1. the border dispute with Russia:
WPR Article | Russia, China End Decades-Long Border Dispute
2. the dispute with DPRK and 1 border dispute with India:
International Boundary Disputes Resolved (Infographic)
That's just 3 examples easily found on the net. Several more border disputes on the PRC's western frontier have also been peacefully resolved (will post links when I have the time to search for them).
Now, what was it about self-determination and respect for international law on the part of PRC again?
--- EDIT ---
I'd like to see a link about PLA submarines passing through Japan's territorial waters. What I have been able to find are PLA warships passing 100km east of Miyakojima island in Okinawa Prefecture:
That's EEZ, not territorial waters. But, if there is a link about PLA submarines passing through Japanese territorial waters, I'd like to see it.