I wouldnt be happy with that.... Is this on both seat bottoms? How about any other metal hardware in and under the rear seats/dash? If you see this throughout, your car may have had flood damage of some sort. I'd want to do some what of an inspection under the carpet/center console. How about pulling the back off the center armrest, below the air vents?
If it is not seen anywhere else, may just be a fluke, as in someone set the seat or pan down during production. I'm going out to look at mine this morning..... At first I thought you were just talking about the frames that mount to the floor. I diddnt look at the seat pans.