Could be the problem with the front of the jacket’s cut? Hard to say really, as I’m not a tailor. He could be styling it a bit more boxy and if he’s not willing to do it the way you want, then time to find a new tailor or at least have a conversation.
Hard to really know w/o photos and such, but it’s probably something you should bring up with the guy altering your clothing. After all, he is working for you in this instance.