There is probably gas connection behind it which also prevents the stove to be pushed allway in. In any case the backsplash is usually cut in line with the countertop and there is always approximately 1 1/2" of space between the stove and the wall.

Some manufacturers make rear extension plates they also sometimes called duct & vent plate so if there is a tiled backsplash which is less in thickness if compared to granite backsplash, the plate helps close the gap between the stove and tiled backsplash for finished look.

Could you get stainless panels for the side of the range?

On another topic, may I ask what your cabinet hardware is? It is really lovely and I am looking for something for my kitchen remodel. I hope you get your issue worked out.

I have seen stainless steel adhesive sheets before. You could adhere that to the sides and camouflage the depth difference a bit.

I just found you post one year later and I am in the same boat today with a new kitchen. What did you end up doing?