AND
A few things. A note that China (or any other nation involved in a dispute or arbitration before the UN or a UN body) submitted to the Permanent Court of Arbitration in the Hague is not at all the same as ruling from that or another UN body. I have included a link to the PCA press release issued regarding the SCS arbitration between the Philippines and PRC
here.
Some of the key findings from the PCA is that the PRC has no valid EEZ claims to areas that the Philippines claims in the SCS since the land areas which China used to make territorial waters and EEZ claims were rocks and not islands and therefore do not grant EEZ areas. The press release also describes what the difference is between a rock and an island, and what is used as the basis to decide the status. The press release also stated that claims had to be based upon the original/unmodified condition of rocks and/or islands, and not on artificial and/or reclaimed islands, or areas that are naturally submerged at high tide.
Now also consider what would be the most logical reasons for the PRC to build 3,000 m airfields (sufficient to take even large aircraft like heavy bombers and strategic airlifters) on built up/reclaimed rocks in the SCS. Such a capability is complete overkill for an EEZ claim, but is quite understandable as a forward operating base for long-ranged MPA, fighter/interceptors, and strike aircraft, as well as land-based AShM and SAM batteries, all tasked with performing anti-access/area denial missions. BTW AA/AD is all about establishing and maintaining control of an area (aka sovereignty) and not about exploiting the natural resources available in a maritime area like an EEZ.
Next, consider
this article which specifically mentions that the PRC did reaffirm a claim of sovereignty over the Spratly and Paracel Islands in 1990.
Lastly, consider both articles like
this one in the Global Times, the significance of what/where it appeared, and what some of it is saying. First, while the article is an op-ed, it is appearing in the Global Times which is a mainland/PRC site/paper with all that implies and entails. In other words, the content had governmental approval even if it was not an 'official' gov't statement or press release.
The op-ed also mentioned that;
This "freedom of navigation" involves being able to have shipping, including naval vessels transit through areas outside of a nation's home or territorial waters as recognized under UNCLOS. Put another way, even if any of the rocks the PRC has claimed, occupied, and built up/reclaimed were used to claim the 12 n mile limit for home or territorial waters under UNCLOS, then foreign shipping and naval vessels can still transit through international waters which after past the 12 n mile limit freely.
If the PRC is advocating and/or acting to put limits on "freedom of navigation" then in essence it is attempting to restrict the ability of other nations to be able to freely transit through international waters and doing so amounts to a claim of sovereignty over the area, as opposed to agreeing that the area is international waters.
As a side note, if one looks through a number of other mainland, PRC newspapers that also have ties the gov't, like being the official paper to the ruling party or other similar and related bodies (like the official paper of the Communist Youth League, etc.) then one tends to see a number of similar or related actions or assertions that amount to the PRC making a claim of sovereignty, even if officials do not necessarily make a direct public statement claiming sovereignty.