And any US SSN stupid enough to come inside the first island chain would just get tailed and destroyed the moment it tried something. China's nuclear subs, especially the SSBN, are basically tech demonstrators to keep the technology alive, it would be an amazing trade to swap 1 091 or 094 for a Virginia.
Yeah, and what will destroy them? Are you sure that they will suceed in destroying them before they destroy Chinese SSBNs? Are you willing to put ultimate security of China on that bet?
You don't build 8 same technological demonstrators. You build one, test it, then another, improved, test it, then next, improved, test it etc. until you are finally happy with the product. Then you start with serial production.