Whats the goal or purpose of the VN reclaimed island(s)?
Land grab for strategic space.
Vietnam is, somewhat rightfully, paranoid about being locked in by China.
If China was concerned about the U.S. threatening its sea lines of communication, Vietnam is in a far more precarious position wrt China doing the same to them.
They want their own SCS fortress islands as a copycat move. That’s something the Vietnamese do a lot btw, for a people who claim to hate everything Chinese so much.
The problem for Vietnam is that they don’t have the naval power of China to adequately protect and back up their island bases, and China has bases so very close that it doesn’t need to reply sole on naval power to attack those bases. Essentially, China is annoyed by the land grabs, but isn’t truly concerned because if push comes to shove, it can easily take those islands by force no matter how much Vietnam builds them up. The only thing Vietnam can realistically do is increase the price a little for China in taking those bases. But the balance of power is so stark that realistically speaking, that will just amount to a higher munitions bill for China.