It's fairly common, or certainly was when your frame was built for the rear brake bridge to rim distance to be greater than fork hole to rim distance. I can't give you a good reason for it, but that's the way it is. It's that way on every frame Ive ever owned.

These days they're usually close enough for both to be within the shoe adjustment range of the same arches, but years ago it was common practice to use longer reach brakes in back.