I half agree with this. I don't think it's worth disclosing UNLESS you have a severe repetition or block. Sometimes people don't understand what is happening, which you can't blame them, and explaining you have a stutter and to bare with eases the tension a lot. Also shows a vulnerable side to you which is great in sales as it helps building rapport. People buy from people and showing a vulnerable side to you really helps to humanise you and separate you from other salesmen!