I think it varies by fabric type. I got corduroy ones in my regular size and did NOT find that they stretched. I ordered a .5 size up and it felt much better in a lacey/crochet size. Maybe check the reviews on the website to see what others say about the particular pair you are interested in?
I got the corduroy ones! I am going to hope they stretch a tiny bit. They fit "ok" now but not loose.