Sometimes designers do this. I am aware that Le Chateau will mark things as a size smaller so the buyer feels better about themselves when shopping at their store but they only provide sizing in Small, Medium, Large and Extra Large.
It's very true. It's a marketing ploy - when women think they are smaller they are more likely to buy the clothes. Sizes used to be Small, Medium, Large, XL, and XXL. Now they're Large, Medium, Small, XS, and XXS. LOL