I cannot imagine much that sounds gross-er than licking my nail polish off between meals because it tastes like KFC. I guess it 'may' be one way to cut down on between meal snacks (or it may just make one hungry for KFC, IF one likes that kind of food).
There used to be (is there still?) a nail polish that mothers might buy to deter their young daughters from biting their nails. It was purported to be bitter so I guess the concept of adding 'flavour' to nail polish is not new but I do hope they have large cautionaries on the bottles to wash hands thoroughly before licking and nibbling.