> many retailers had no measurements for their own clothes except the reference size.

When you say reference size, do you mean like a single size which is used in the industry for samples? I had a friend living in Montreal who was fashionable, she said it was like heaven being a size 8 in Montreal because she had access to a bunch of cheap, interesting, one-off samples. Wondering if this is the same concept.

Never been in the industry, but used to follow a blog of someone who did pattern design for a north-american casual-wear company, super interesting stuff! There's lots of nuance in size grading.