Yumcha places use cheap south fujian wulong since many years now. not shuixian. before this they used cheap shuixian, not from wuyi. 
do not order shuixian in restaurant now. very bad quality oolong, maybe too much pesticide. no good for health. order sou mei, more safe.
Always buy good shuixian from good teashop, not restaurant. I sell. I know.
