China does promote potatoes. But the key advantage of the potato is that it grows where rice will not, in the drier and colder west of China. So it allows China to expand its food growing capacity.

Unfortunately, while I had plenty of good experiences with food available in China, it was my experience (2018) that the restaurants just didn't know what to do with potatoes; they were usually served like a turnip or carrot or something, and not treated as a starch. It probably doesn't help that most of the potato dishes that Westerners adore involve dairy products or olive oil in some way, when these are not so accessible in China.

Are potatoes healthy, anyway? I adore them, but they cause trouble (gas, fermentation) and they seem to be excluded from many kinds of health diets.

(The again, most nutritionists seem cargo cultists to me)