I have in my notes (from Beyond the Great Wall) that the Uyghur people living in Xinjiang "are now primarily Sunni Muslims", but I couldn't find anything online about the particular Sunni Muslim view of alcohol, so no help there.

I suspect the answer may actually be, as I speculate to pandarus above, that the use of beer/wine in some of these recipes is simply a modification made as the dish spread across (and outside) China.