When the 3 was in design the original seat spec was really nice, in fact way nicer than any S seats and a decision was made to "dumb them down" so the car would not look nicer. The cost was not a factor but many things were much nicer than the S. Unfortunately I guess there needs to be segmentation.
My VIN is 14928. I have the new Gen 2 seats in front and the old Gen 1 seats in back. This mix is of no concern to me. This car is so amazing that I'd be happy with it even if it had Chevy Bolt seats.
Mine is in the 4xxx range and I think the front seats are fantastic... though I admit to rarely ever being in the back ...