How recent was this? Years ago I remember hearing the scenario where people who switched from iPhone -> Android (keeping the same number) would continue to have iMessages go to their old phone. Or the messages would just get lost in the ether if their old phone was off or sold.

For awhile, at least at the Apple store, they were very deliberate about disabling "Find my iPhone" and iMessage when handing off or wiping a phone. I don't remember them doing this recently, so I figured it was built into the process now.

I do think we need some basic awareness about digital devices, just like people do when they let someone borrow the keys to their house (although, many people are terrible at managing that). I recently sold a house with a Nest and a few other IoT things. I wiped them and reset them to factory settings. The realtor and new owner were asking me for my login/password (I'm sure this happens often for them) because they figured it was still tied to my old account.