I found some online timatic sources stating that nationals of US or Canada are not permitted to use the multiple-stop transit within China, if transiting through Weihai (WEH) or Wuhan (WUH) only. So presumably Tianjin (TSN), Xi'an (XIY) and Zhengzhou (CGO) are okay for 72 hours TWOV now? If confirmed the wiki will need to be updated.