It's possible because stutter varies a lot depending on the context. I know that's not a very detailed answer, but that's all we get for now (pending whatever research will be able to uncover more). It's my impression that stutterers experience intoxication differently. For my own part, I've had times where it "helped" and times where it certainly didn't help at all. I think it's more within stutter variance generally, and not so much intoxication specifically...