Believe it or not, vodka has standards. The smaller offerings of Skol dont fit them and instead of saying "Vodka" on the bottle, they swap the word with "Premier". Vodka doesnt appear on the bottle.

The theory with the liquor store bros is people buying the big bottles actually kinda care so they put effort in it to make it legally vodka, and people buying the half pints just want to drink the whole thing at once no matter what at the lowest possible cost so who cares if it has effort, so the smaller bottles are just whatever.