Well. It is true but but looking at it from a naval point of view, unlike the SCS, none of them have an ideal seabed like the Sunda shelf with the right sea depth that will allow the marauders to rest and hide until they are discovered.
Erm, seabed argument is mostly for conventional subs. Nuclear submarines normally can't lie on the bottom, unless specifically designed for it.
For nuclear submarines, as a rule of thumb, deep water=good.
Thus there are already absolutely ideal positions right behind 1st Chain - an absolutely enormous swatch of sea no ASW can properly lock, yet protected by that chain from any consistent Chinese ASW, yet covered by lots of convenient islands(often mountainous) from too early detection of launch, yet almost always with enough weather patches to interfere with space-based IR/Optical observation and early warning assets.
Importantly, key targets for immediate suppression (political centers, C&C, etc) are either very close(and there are better means to strike them compared to ballistic missiles), or are relatively far from SCS - i.e. other strike locations are more advantageous from this point of view, too.
That is why earlier USN was conducting a survey of South China Sea with underwater drones. They have a definite plan but China 7 islands strategy is a spoiler.
SCS is by now
the main hub of Chinese naval activity(not even one of anymore), the bastion of Chinese sea deterrent, and a starting point of PLAN SSN deployments.
USN SSBNs don't need to be a reason...