I have done that actually. The sizing seems quite different to me. I seem to wear a size or even 2 sizes bigger in other French clothes. I thought maybe H sizing was somehow different!
The sizing of Hermes clothes is all over the place I have found.. Some RTW runs true to size, some smaller some larger
My suggestion is to just try what you like & go from there
I just purchased 2 dresses & took a different size then expected... go figure LOL