In my experience, only the bottom ends of the BF flatware are magnetized. This being the case, it seems unlikely that this would occur accidentally or inadvertently through magnets being used in the waste recovery process.

It seems to me that a much more likely explanation is that it makes the clean flatware as it's handled by the flight attendants easier to handle. When the flatware is given to the passengers, all items needed for a particular meal are enclosed in a folded napkin, with the tips of the flatware exposed, and all held loosely together with a plastic clip (this can include 2 forks, 2 knives, and a spoon, perhaps more depending on the meal). By having the bottoms magnetized, they'll tend to stick together, making it much more unlikely that a single piece will fall out.