Dual citizen (not Chinese) conflict with alipay/immigration?

A longtime US citizen with recent NZ citizenship in addition is traveling to China on the NZ passport to allow a longer 20 day stay without a visa that NZ passport allows.

For alipay though should he use his US passport as his bank cards are verified by his US passport?

Is that going to cause problems, traveling on the NZ passport, but buying things in China on the US ID?