Is it a surveillance tool for cash payments? Yes:

“ Xu Yuan, associate professor at Peking University’s national development research institute, told broadcaster CCTV that because cash transactions were offline and transaction data from existing payment platforms was scattered, the central bank was unable to monitor cash flow in real time.

“Although there is little change from the perspective of user use, from the perspective of central bank supervision, future forms of finance, payment, business and social governance etc, this is the biggest thing ever.”