it is very possible to have the narrow tire on the wider rim. If you go on tirerack and look up the tire brand and line, you can go to specs to look up your size, and it will tell you the range of widths that it can fit on.

most likely, the previous owner preferred to allow front/rear rotation of tires to even wear, but the dynamics of the tire will be different, as the different wheel widths will change the geometry of the tire.

I would stick with the proper tire sizes (255/285) next time around, or get matching pair of wheels to keep a square setup (all 4 wheels the same)