I think this is good practice from repair people: my motorbike mechanic would always keep the old parts when replacing them, to show me the status when I was taking the motorbike back. It’s a sort of transparency move that I actually appreciate.
And moreover, the old part is still yours, so it makes sense to give it back to you, unless you explicitly say otherwise
I didn’t know about this series, thank you! I will try watching it
Edit: 🤬 not available in Italy