Politico has an article about what happened on the trips Walz led that took high school students to China. The article, if accurate, suggests Tim Walz is somewhat fluent in Mandarin.
A web search turns up a BBC article which reveals that for a year in 1989 before his marriage, Walz lived and taught (English?) in China. This explains (a) how he learned some Chinese and (b) the choice to return there on the Walz honeymoon.
Chinese schools were desperate for teachers of English at the time. In 1986 the DrsC toured in China and were both offered jobs+housing on the spot. We declined the offer.
Should we suspect a Manchurian Candidate (1962)? Probably not, but likely a friend of China. We got a taste of the expat experience during a year on Guam; it can be very interesting.
We still have warm feelings for Guam and have since gone back twice to visit. However Guam is not an adversary and potential enemy of the U.S., while China is exactly that. It is entirely realistic to question whether Walz is willing to act against Chinese interests.