I took some photos of my pews
these are the pews I got with mismatched ends that had to be remortised to accept the seats and back that were a match.
I made templates off the seat and back and you can see where they have a reverse curve. The bottom is straight but the seat top has the reverse curve. Hope it all shows in the photos:
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)