Near as I can tell the Kalina is still just a paper project.
If the offer was real and official, it seems more like a fishing expedition by the Russians to try the get the Chinese to help finance the development of this proposed new class.
To be honest, I'm not too sure the Russians hold much, if any, lead on China when it comes to conventional AIP subs, and with the trend in new Russian defence projects recently, by the time the Kalina is operational, China will probably have a better indigenous equivalent, if it doesn't already.
Russian offering to share nuclear sub technology with China would be a huge deal, as I think that is an area where China currently desperately needs to reform as there is a lot of entrenched interests using the necessary secrecy and high security of such strategic assets to effectively monopolize the market and protect ineffective individuals and organisations from any sort of real competition. Thus this removes almost all pressure for them to get their act right, which is why China's nuclear subs are still such a weakness.
I know for a fact that China has world class engineers and designers who proposed cutting edge nuclear sub designs and concepts way back in the late 90s and early 2000s which are only just coming online in the latest US and European classes. Had their proposals been given serious consideration, Chinese SSNs and SSBNs are almost certain to be far better than what they are now, and may well have closed the gap with the most advanced American and European classes to a generation or less.
The current Chinese nuclear sub maker is very similar to SAC back in the 90s and shares most if not more ills. But unlike the aviation industry, China's nuclear sub section only has one player , so there was never any real way the anyone could force it to shape up or have a realistic alternative the PLAN could turn to.