Same issue here.I can confirm that it worked correctly in the end of October as we just did extensive testing and launch of this feature. Everything was working on 20th of October and it stopped work after 8.11. We haven't had any orders in between, ...

We have exactly same issue and it started in November.Bigger thread linked to the same issue is here: https://community.shopify.com/c/shopify-apps/shopify-post-draft-order-not-respecting-passed-shipping-line/m-p/2306305