You could certainly crop in post instead, but it's awfully convenient to frame to way you want while actually shooting. And it only takes a beat the change the crop mode - you can assign the function to a button. I love the way the GR can be used entirely with one hand.
I believe, though it's been over a year now since I bought one and then sold it, that the crop affects jpeg but not raw? You can shoot in both, frame how you want in 35mm (28 was too wide for me too) and then have your backup raw file which will be 28mm. Someone correct me if I am remembering wrong..