Patternmakers for womenswear are really experts in curves.
Nothing on a woman’s body is flat and almost nothing on a pattern is either. Patternmakers understand the relationship between body curves and pattern curves and can recognize when they aren’t matching up.
The curves go beyond the simple measurements of a spec sheet and really shape the fit of the garment.
Have you ever received a sample that matched all the requested measurements, but just didn’t fit quite right? The issue is most likely in the pattern curves.