South China sea shoal is a treacherous region.

https://sg.news.yahoo.com/philippines-extricates-warship-south-china-sea-shoal-232756352.html

Philippines navy got grounded in the South China sea shoal which showed that its navy didn't have an in-depth knowledge of the shoal region.

We had stated previously that the South China sea shoal was a treacherous region and no commercial shippers would want to sail there.

http://sg-stock.blogspot.com/2017/01/lets-stop-harping-on-south-china-sea.html

Thus, it is pointless to promote freedom of navigation in such a treacherous region and doing so would cause harm to the commercial shippers.