Apaprently they don’t want it to be disputed for much longer.

That’s kinda what I was thinking. The general concensus seems to be “whatever they built it for there are easier ways of doing it” but I think in the end you don’t spend that kind of effort on a whim. If I were India that would definitely be a concern in my book. One gets the impression that China is determined to get it’s hand on every scrap of land it can no matter how spurious the claim.