>>>>>things catered for one flight are only good for that flight and no other...

It makes sense that they remove all the carts, and don't leave items on the plane. They can then sort them out and restock them with the right counts, while loading the aircraft with already restocked carts. I've also heard that any wine bottle opened gets tossed upon arrival, even if just one glass was poured. But all unopened items in the carts exchanged upon arrival getting tossed? That would be kRaZy!