Yes thats why is was baffled why China stop building their man-made islands, they built so few.The 9 dash line claim, predates even before the UNCLOS. UNCLOS was established in 1980s while the 9 dash line claim was published even before PRC government was founded in 1949.
So the UNCLOS is trying to implement a change to an already defined, claimed and published maritime boundary. Its no wonder why China did not bother to spend or send anybody in the 2016 arbitration. They see it as moot point.
Majority of the smaller countries which have claims in SCS view their claims for economic reasons, like fishing rights, or oil/gas exploration. China on the other hand, when the 9 dash line was claimed and published, did not view it for economic benifits. I mean what level of technology China had in 1947(when the claim was published) for oil offshore exploration? The Chinese leadership at that time had a foresight, that because of the encirclement of US around China, China must have a breathing space in the future conflicts. They view the SCS as strategic, existential claim.
And it is even clearer now. Countries that are very far away from China like UK or US or even France are sending their warships in SCS for lame freedom of navigation reasons and for what? The Chinese remember very well, how much these foreign naval powers incursion can do damage if they dont stand up against them. This is just almost a repeat of the 8 nation alliance invasion in China in the 19th century.
So China must hardened its position in SCS, in order to overcome the humilation it endured from foreign powers for the past 200 years.
They should have built at least 15-30 more.in different locations to choke off entry to the SCS and make any naval intrusion there impossible.
I mean when China had already taken a reputation hit due to building their island they should go all the way to the end and build everything rather than this half-job they did