Production Standards
One my of favourite retail stores to shop at is at Aritzia . Their Babaton brand carries the Bennett dress in their collection and the silk dress has a super flattering fit for all body types. I have tried on this style dress in various different colours in the same size (size xs) and have found a different fit. I definitely think the 1/2" tolerance applies here, especially in the case that the same style dress is made of different prints or colours even though the material is the same (silk in this case).
Check out below for side by side comparison of a plain colour Bennett Dress compared to one with floral print. I personally found the burgundy colour one a bit more tight fitting, but it is not that noticeable when worn as you can see below. I definitely feel more comfortable in terms of sizing in the navy with floral print dress.
Through this experience, I have learned that if the tolerance is too high where it is noticeable to the shopper, it makes it hard to shop for item online, especially return policy are not as customer friendly, as it makes try-on necessary in order find the proper fit. Inconsistent sizing for a staple item in a collection definitely can frustrating and ultimately negatively impact the customer experience.