This is just a sensor network.
If China's massive SSK fleet presents as a credible threat against USN, Japan's SSK fleet is definitely a threat to PLAN surface ships. Previously, China's main weakness beyond the first island chain is countering the air threat and the SSN threat. The air threat is being countered symmetrically with PLAN and PLANAF's own air power. The subsurface threat is a bit of an unknown. SSN and SSK numbers and technologies have come a long way but PLAN's massive surface build up can still be threatened unless its ASW is absolute top notch, second to none.
The sensor networks and UUVs are one part of the ASW puzzle but how well practised is PLAN really in ASW? Japan and the US have some of the world's best SSK and SSNs.
I think it's important to not equate SSK to SSN. The threat level posed by Japanese subs and American subs are really not in the same order of magnitude.
Yuan subs are essentially good for just ambushing against US Navy btw.