Well, let's think this through... assuming chickens have alcohol dehydrogenase's....liquor's active ingredient is ethanol. Ethanol will be adsorbed by the body and mostly and metabolized by the liver which produces alcohol dehydrogenases... so you could start the process of cirrhosis and fatty liver syndrome before you butcher the bird. I suppose if you like eating fatty livers and gave them enough ethanol you'd have a tasty fried fatty liver, but why waste the ethanol? These birds already eat so much so fast with corn laden food, by 8 weeks old they probably already have yellow fatty livers.
Ethanol is metabolized VERY fast.... so can't be for flavor, and rigor is a whole different beast in a live animal or fresh kill. That is based on ATP supplies in the muscle, or rather, the lack there of when something dies.