Reproduce: https://global-search.toolforge.org/?q=.*&regex=1&namespaces=&title=MOS%3A.*

Expected: It can find pages listed in https://zh.wikipedia.org/wiki/Special:%E5%89%8D%E7%BC%80%E7%B4%A2%E5%BC%95?prefix=MOS%3A&namespace=0 (there are more than 200 of them).

Actual: The result list no pages in zhwiki (see also T363538#9747595).