It certainly will relax with use. I’ve found that any firmness that nappa and suede have when new and unhandled will disappear fairly quickly with use. What I did to reduce the wide east-west effect when mine was new was to put my usual stuff inside, push the center-zipper area down to expand the armhole opening, then simply use the bag. At first, I had to push that part down every time, but at this point, mine has been trained to take that shape when my stuff is put inside.
Some here have suggested loading up the bag with soup cans and leaving it to hang, but I’ve never had to resort to that with any of my BVs (and I didn’t want to risk misshaping my bags that way, either).