The fact that they launched the missile from shallow depths within Bohai shows that China is planning for worst case scenario if the nuclear subs can’t make it to deeper water in SCS.
Reminds me of the Soviet navy's creation of the SSBN bastions in the arctic Laptev,Kara,Barents seas where the Russian Tyhoon,Delta 4 series SSBNs can remain safely in their waters without traversing NATO/US chokepoints/SOSUS networks and as the SLBM technology can provide the necessary range /accuracy/numbers to make it feasible.The SCS is viable but the Gulf of Bohai /Chihli is way too shallow. for a PLAN ssbn bastion.