No, this is nothing new. The territory claim in SCS goes back 100 years to the Republic of China (aka Taiwan) and after Communist won in the civil war in 1949 they simply inherited the claim.
It was originally a larger claim of 11 dash line, but China after discussion with Vietnam reduced it to 9 dash line in 1952. It Vietnam was hosting a military bases of China's enemy and not a neutral country the time, it is unlikely China would've reduced it, maybe they would've expanded it to cover more of Vietnam like they did with Philippines. It is common knowledge China have painted Philippine bases hosting US missiles as first strike targets.
As I said, history has shown less powers fared most well between major powers when they stayed neutral, this is just fact. If Ukraine stayed neutral and didn't f*ck around to join NATO or EU nothing would've happened. When you take a side, you make an enemy on the other side by default.
Having an equal partnership is good alliance, but an unequal partnership with a stronger power is will always result in the weaker party being taken advantage of.
