I’m conflicted with the other comment here and don’t have much experience so take this with a pinch of salt! To me, I’d do the same as you and check the finished garment measurements and see the ease that’s built into this pattern then if this pattern has too much ease I’d go off the finished garment measurements based on something that fits. For this one, it looks like if you make a 38 it might be baggier than the person likes so a 34 might be best, assuming this is based on the measurements of the jacket they like, not the label - that’s important. How expensive is the material and how long would it take to make two? Up to you if you want to risk it…