Currently, Google is unexpectedly indexing /zh/ language variant URLs instead of /wiki/ links for Chinese Wikipedia.
A quick example is: https://www.google.com/#q=汉语+wikipedia
As you can see, the first link's URL is https://zh.wikipedia.org/zh/汉语 and lots of other links with /zh/ URLs.
If you open it and check its source, it says
<link rel="canonical" href="https://zh.wikipedia.org/wiki/%E6%B1%89%E8%AF%AD" />
So since the "canonical" version is /wiki/ links, Google should follow and index it instead. But at the moment it's not for some reasons.
The most weird part is, if you search with "site:wikipedia.org": https://www.google.com/#q=汉语+site:wikipedia.org
Almost all the links in the first page suddenly became /wiki/ links (correct behavior).
The problem of /zh/ links is that they ignore user's language variant settings. I need to manually change to /zh-cn/ or /zh-tw/ variants after clicking a link from Google (which is a very common scenario). For /wiki/ links, they would automatically jump to the variants according to user's' preference.
It has been like this for months if not years. I have no idea if it's on Google or Wikipedia. I asked several times on zh.wiki but none takes responsibility or has the ability to fix it.